Was it in reference to Jews? To capitalism? To Britain? To isolationism?
These are the only significant mentions (in order of appearance):
EDIT: Readers should know that "the war" is generally the First World War.
Many contemporary European States are like pyramids standing on their apexes. The European territory which these States possess is ridiculously small when compared with the enormous overhead weight of their colonies, foreign trade, etc. It may be said that they have the apex in Europe and the base of the pyramid all over the world; quite different from the United States of America, which has its base on the American Continent and is in contact with the rest of the world only through its apex. Out of that situation arises the incomparable inner strength of the U.S.A. and the contrary situation is responsible for the weakness of most of the colonial European Powers.
England cannot be suggested as an argument against this assertion, though in glancing casually over the map of the British Empire one is inclined easily to overlook the existence of a whole Anglo-Saxon world. England's position cannot be compared with that of any other State in Europe, since it forms a vast community of language and culture together with the U.S.A.
On the other hand, British and American war propaganda was psychologically efficient. By picturing the Germans to their own people as Barbarians and Huns, they were preparing their soldiers for the horrors of war and safeguarding them against illusions.
History furnishes us with innumerable instances that prove this law. It shows, with a startling clarity, that whenever Aryans have mingled their blood with that of an inferior race the result has been the downfall of the people who were the standard-bearers of a higher culture. In North America, where the population is prevalently Teutonic, and where those elements intermingled with the inferior race only to a very small degree, we have a quality of mankind and a civilization which are different from those of Central and South America. In these latter countries the immigrants--who mainly belonged to the Latin races--mated with the aborigines, sometimes to a very large extent indeed. In this case we have a clear and decisive example of the effect produced by the mixture of races. But in North America the Teutonic element, which has kept its racial stock pure and did not mix it with any other racial stock, has come to dominate the American Continent and will remain master of it as long as that element does not fall a victim to the habit of adulterating its blood.
Only by adopting these achievements as the foundations of their own progress can the various nations of the Orient take a place in contemporary world progress. The scientific and technical achievements of Europe and America provide the basis on which the struggle for daily livelihood is carried on in the Orient. They provide the necessary arms and instruments for this struggle, and only the outer forms of these instruments have become gradually adapted to Japanese ways of life.
There are territories where the Aryan can establish fixed settlements by means of the technical skill which he has developed in the course of more than a thousand years, even though these territories would otherwise have to be abandoned, unless the Aryan were willing to wander about them in nomadic fashion; but his technical tradition and his age-long experience of the use of technical means would probably make the nomadic life unbearable for him. We ought to remember that during the first period of American colonization numerous Aryans earned their daily livelihood as trappers and hunters, etc., frequently wandering about in large groups with their women and children, their mode of existence very much resembling that of ordinary nomads. The moment, however, that they grew more numerous and were able to accumulate larger resources, they cleared the land and drove out the aborigines, at the same time establishing settlements which rapidly increased all over the country.
It is revolting to think how much damage is indirectly done to German prestige to-day through the fact that the German patois of the Jews when they enter the United States enables them to be classed as Germans, because many Americans are quite ignorant of German conditions. Among us, nobody would think of taking these unhygienic immigrants from the East for members of the German race and nation merely because they mostly speak German.
If the number of important discoveries which have been made in America has grown considerably in recent years one of the reasons is that the number of gifted persons belonging to the lowest social classes who were given a higher education in that country is proportionately much larger than in Europe.
At present there exists one State which manifests at least some modest attempts that show a better appreciation of how things ought to be done in this matter. It is not, however, in our model German Republic but in the U.S.A. that efforts are made to conform at least partly to the counsels of commonsense. By refusing immigrants to enter there if they are in a bad state of health, and by excluding certain races from the right to become naturalized as citizens, they have begun to introduce principles similar to those on which we wish to ground the People's State.
But the theoretical formula is not wholly put into practice by any confederacy that exists to-day. And least of all by the American Union, where it is impossible to speak of original sovereignty in regard to the majority of the states. Many of them were not included in the federal complex until long after it had been established. The states that make up the American Union are mostly in the nature of territories, more or less, formed for technical administrative purposes, their boundaries having in many cases been fixed in the mapping office. ... Consequently, in speaking of the United States of America one must not consider them as sovereign states but as enjoying rights or, better perhaps, autarchic powers, granted to them and guaranteed by the Constitution.
Thus the political results of the war to prevent the development of German power was the creation of a French hegemony on the Continent. The military result was the consolidation of France as the first Continental Power and the recognition of American equality on the sea. The economic result was the cession of great spheres of British interests to her former allies and associates.
There is not any British, American, or Italian statesman who could ever be described as 'pro-German'. Every Englishman must naturally be British first of all. The same is true of every American. And no Italian statesman would be prepared to adopt a policy that was not pro-Italian.
The gigantic North American State, with the enormous resources of its virgin soil, is much more invulnerable than the encircled German REICH. Should a day come when the die which will finally decide the destinies of the nations will have to be cast in that country, England would be doomed if she stood alone.
He already sees the present European States as pliant instruments in his hands, whether indirectly through the power of so-called Western Democracy or in the form of a direct domination through Russian Bolshevism. But it is not only the old world that he holds in his snare; for a like fate threatens the new world. Jews control the financial forces of America on the stock exchange. Year after year the Jew increases his hold on Labour in a nation of 120 million souls. But a very small section still remains quite independent and is thus the cause of chagrin to the Jew.
Looked at purely from the territorial point of view, the area comprised in the German REICH is insignificant in comparison with the other States that are called World Powers. England must not be cited here as an example to contradict this statement; for the English motherland is in reality the great metropolis of the British World Empire, which owns almost a fourth of the earth's surface. Next to this we must consider the American Union as one of the foremost among the colossal States, also Russia and China. These are enormous spaces, some of which are more than ten times greater in territorial extent than the present German REICH. France must also be ranked among these colossal States.
For the future of the German nation the 1914 frontiers are of no significance. They did not serve to protect us in the past, nor do they offer any guarantee for our defence in the future. With these frontiers the German people cannot maintain themselves as a compact unit, nor can they be assured of their maintenance. From the military viewpoint these frontiers are not advantageous or even such as not to cause anxiety. And while we are bound to such frontiers it will not be possible for us to improve our present position in relation to the other World Powers, or rather in relation to the real World Powers. We shall not lessen the discrepancy between our territory and that of Great Britain, nor shall we reach the magnitude of the United States of America. Not only that, but we cannot substantially lessen the importance of France in international politics.
As I said, there are a few more references, but mostly to things like, "the American, Woodrow Wilson" or there's one to an anti-German propagandist living in the US. But otherwise, this is basically it. You'll see that he discusses it somewhat, but it's hardly frequent in the some 650 pages that make up the book. I think most people would be surprised that he's generally favorable toward the US. Yes, he thinks it's controlled by Jewish capitalists, but otherwise, his references are mostly either positive or at least neutral.
EDIT: formatting. Oh, and my pdf of Mein Kampf doesn't have page numbers, so sorry on that part. But googling the quotes should bring up the page numbers easily enough.