I love what America was supposed to be, and maybe by becoming an American I can, in some small way, help shape it more towards those lofty, and possibly unreachable goals. Does that answer satisfy?
You're making excuses... for which there is no need.
If your real goal was to make the country better, to move it toward an ideal, you'd be far better moving to some African and Asian country, where your efforts to improve the place would be much more likely to be effective, saving many more lives, for example.
The truth is that you came to America to improve your own life. So what? That's what America is
for. The genius of America is to realize that when people do that, they, on the whole, make the
country better much more than the usual country-improvers and utopia-chasers.
An immigrant who came to America and opened a deli improves the residents' convenience in the neighborhood where it's opened, thus improving America. A professor who flies in to give lectures about "the awful horrific American imperialism" or "How to defeat American militaristic chauvinism" or similar attempts at "improving" America only "improves" his own ego.
P.S.
As an aside, these folks, by the way, are typically contemptuous of the working-class deli-opening guys, in whose name they claim to speak. I cannot see why. It's easy to teach a deli owner to give passable lectures on "the Marxist-feminist criticism of American capitalist imperialism" (or the equivalent). It would be a rare "American studies" professor indeed who could run a deli without the deli losing most of its customers within a week and going bankrupt in a month.