You can probably get twice-cooked pork anywhere in Europe and in every city in the US with more than 40,000 people in it (ie: everywhere). But it is absolutely a Sichuan Chinese dish, regardless of its universality.
If you define "true" American cuisine as something that is (a) only eaten in America and (b) eaten consistently throughout America, you've come up with a definition that probably nothing fits. Though: watch the British Bakeoff episode where they attempt brownies, one possible contender.
Lots of stuff is probably only gettable in America! I doubt you can get a good cheese steak, italian beef, po' boy, biscuits & gravy, or scrapple in Europe. But you can't get a good version of all of those in most places in America, too.