Always more than can be said, but do check out this old answer from /u/restricteddata, and his related blog post.

Yes. The USA would have been willing to consider the use of nuclear weapons against Germany, had it come to that. The Soviets and their massive pressure from the Eastern front, coupled with the rest of the alliesd forces hammering in from the east, brought an end to the European conflict before that "final option" needed to be (or was even ready) to be employed though.

In May of 1943, the USA had what at the time was a highly classified meeting amongst their military and political apparatus that focused on this issue - focusing on what they called at that time the "Oppenheimer Project" or the "Los Alamos Project", which was the potential requirement or use of these weapons of mass destruction. This meeting concluded with the idea that Japan was the preferred option, because it was deemed at the time that, if used, the Japanese would be able to glean less data from the detonation of the device than the Germans might. The Germans had a relatively advanced nuke development program of their own at that time, and that was taken into account by the Powers That Be in the US. To quote the above linked report directly, when referencing the hypothetical use/detonation of this brutal weapon that was nearing completion - "The Japanese were selected as they would not be so apt to secure knowledge from it as would the Germans." If the first weapon was a "dud" and failed to detonate correctly, it was very worrisome to the USA that the dud residue could potentially give the Germans a lot of intel and evidence that could help their own nuclear program out, and the Germans were deemed, by American and British intelligence, to be a a lot further along than the Japanese were in their nuke development.

However, this does not mean that Japan was ALWAYS the ONLY target predestined for the use of nuclear bomb(s). It meant that, in 1943 when that report was penned, that Japan was deemed as the best target strategically at that time, but certainly not the only one. Germany was still very much on the table as a target as well, and it would remain to be seen how D-Day (July of 1944) turned out and how well that planned allied invasion of Fortress Europe played out. As history shows, D-Day at Normandy was a powerful success for the allies, and gave them a required foothold into the European theater to press the Nazis from the west while the Russkies hammered and advanced on them from the east, and that sandwiching and crushing of German forces thankfully rendered the requirement for the use of nuclear weapons null and void in that European theater. Germany was always a potential target though, especially if D-Day had failed, and because it was well understood that the Nazis were seriously working on a nuclear weapons program of their own that needed to be squelched. While being short and to the point here, I do not think many WWII historians would disagree with what I just said there.

In May of 1945, a few months before Hiroshima and Nagasaki and just as victory in Europe was finalized, there was another meeting in the US that has been generally and officially referred to as the "Target Committee" meeting. It focused on how and where to use the "gadget" (the nuclear bombs, both gun-type and implosion-type) and how and why they would be employed. This was right around V-E Day (Victory-Europe) and the defeat of the Nazis remember. At that point though, the defeat of the Nazis in Europe was essentially seen as clear and assured by the allies, so they focused their targeting plans entirely on Japan for the nukes they had (or felt they were soon going to have) in their arsenal.

Germany was always on the table for a target though throughout the Manhattan Project, right up until V-E Day. German soil was not nearly as palatable a target as Japan was though in the American's minds. That is clear, but if the President (FDR) had of demanded it, Germany would have been struck with nuclear fire if the weapon was ready and Germany had not surrendered by that time. It was always a strike option that was on the table. According to General Leslie Groves (military director of the Manhattan Project), in his memoirs, he states that he had a discussion with President FDR in late-1944 explicitly about using "the gadget/bomb" against Germany if needed. General Groves was largely against the idea for a host of reasons, but admitted to the President that if need be, we can do it, and President Roosevelt took that under advisement, and it was actually the President who asked about it as an option. To me, that says the Pres' was thinking about it, and wanted military advice about it, should the need arise. Thankfully, the need never arose though, as the allies were able to suppress and defeat Germany using conventional forces alone.

So much of the answer hinged on President Roosevelt's mindset, and again, according to General Groves, the President was prepared to, if needed, use that horrific weapon on Germany to try to end the war if it came to that. Thankfully, the success of D-Day on the western front and the Soviet advances and victories on the Eastern front meant that the option of nuking Germany was never needed to be seriously considered, but it was still very much was on the table as a consideration, and was clearly in President Roosevelt's mind right up until V-E day.