Anything post 19th Century?
That wasn’t the question you asked.
It’s bad netiquette to change your question, or move the goal posts when you get an answer you don’t like to your original question.
As for the 20th century, the argument can be made that America’s association with oppression was worse than in the 19th century. Largely as a result of our becoming an economic empire in the 20th century, with all the commensurate economic, corporate, and political interests that come with empire.....and which are generally elevated over the concerns of human rights and social welfare of other people. Particularly brown people.
I’m not surprised a conservative like you, in the tradition of appalling dunces like Ronald Raygun and George Dumbya Bush, view America’s history through the lens of a John Wayne movie, where freedom is always on the march, led gloriously by the stars and stripes.
No doubt our defeat of the Nazis was, broadly speaking, a win for humanity and decency. But 20th century America, in the broader scheme, was quite closely associated with oppression and neo-fascism. As a rightwinger, you probably aren’t aware of our numerous invasions and occupations of Central American and Caribbean countries, which resulted in the installment of rightwing dictators who were friendly to American corporate interests, but had little to no resemblance to the ideals of a Jeffersonian democracy.
Further, the greatest conflict of the latter half of the 20th century was not fought by American and soviet armies. But, by our proxies. Often, despotic rightwing proxies. And quite unlike the John Wayne movies Ronnie R. was fond off, we invested a lot of our effort in the Cold War, overthrowing democratically elected regimes, in favor of despots and dictators who would do our economic and political bidding.
American exceptionalism is a quaint notion, which is mostly fodder for 9th grade American history classes. Other nations do it too, its quite unexceptional. It's not just us. I’m quite sure Japanese school children are not taught about the rape of Nanking, and I’m sure German school children are given a relatively sanitized version of their Fascist and imperial history.