The thing is, the US did pursue territorial expansion throughout its lifetime, and quite blatantly up through the first half of the 20th century. Manifest destiny is an excellent example of this. While the land in the west was never treated as a typical colony purely there for economic gain for the state at the expense of the local populations and nations, as the British and Spanish often did, it was nevertheless frontier territory that the United States put under its own protection for its own use and gain. During the Spanish-American war, the United States gained extremely valuable territories from Spain, including Porto Rico (an excellent place for growing certain crops that were not able to be grown in many other places in the US) and the Philippines (an extremely important series of islands for US trade that served as a shipping stop for ships traveling across the Pacific Ocean). And while these territories were not called “colonies”, they were very often treated in the same manner that other “great powers” at the time treated their colonies.

During the end of the 19th century and the beginning of the 20th, it became clear that American influence in the world came not from military supremacy but from diplomacy, banking and economic partnerships. This is why the United States decided to, at the time, seek out economic relationships across the world rather than invading and gaining vast territories to use as de facto colonies. The US only expanded its economic influence after WWI and WWII, as the combatants in the eastern hemisphere were greatly starved for both cash and recourses. Thus, the US ended up on a path of global economic control and supremacy in the middle of the 20th century.

Now we get to the “interventions” era, which is pretty much an ongoing period since the end of WWII where we can see the US interfering through espionage, blackmail and military force in the affairs of other nations to, quite bluntly, do as they are told. Both the US and the USSR has a hand in this throughout the world. This led to a unique form of American colonialism, with an even closer economic partnership with western countries (plus countries like Japan, South Korea, etc.) as well as, perhaps most importantly, the permanent stationing of troops on foreign soil, all of which we continue to see today.

At present, the United States can be said to continue this “neo-colonial” expansion into other countries over which it had very little influence before, such as those previously in the soviet bloc. Though it had the opportunity to pursue a great land empire across the world like its European counterparts, it chose to follow a path of economic and political influence instead, which all leads into the current global geopolitical situation that we can see today.