OP, it seems obvious that your palate is geared towards American preparations, but I agree with your premise. (Although I strongly disagree on the Italian chains that you cite, which I find terrible.)

America really has the best of everything. If you attempted to find the best Italian food in Chicago, French or Chinese in New York, Mexican or Korean in Los Angeles, etc., or even in secondary or tertiary cities, I believe that you would find something as good as the best in the local country. I have enjoyed the Chinese food in New York and San Francisco as much as Beijing and Shanghai. And don't forget what you might call modern American food (e.g., Vidalia, Charlie Palmer Steak, or 2941, to use Washington, DC as an example), which in my opinion compares to the best local cuisine in any other country.

For less globalized cuisines like Arabic, Spanish, or Polish, I don't know how America compares. Then again, these cuisines are not that great, anyway, which is why they are not globalized.

When it comes to the average restuarant in the U.S. versus the average elsewhere, I would not say the U.S. is the best. I vote for Paris, among the places that I have been. Of course this is partially due to the novelty and to my personal preferences, but I have found every little brasserie, corner bar, train station, even the sandwiches at the deli counter in the department stores, to die for.