I think that "country X vs Y" stuff is much of why, when an American is ignorant about facets of another country/culture, they don't default to feeling like they are in some way at fault for that ignorance. That isn't the same thing as being proud of their ignorance (which is around in America, but much less common than one might fear), it is a reasonable position to have.
Any time spent learning about the details of some other culture/country is time not spent on learning about another. Faced with the abundance of sets of details to learn, and with little to make one country/culture's set of details stand out as the one an American might want to learn, lack of self-recrimination is a pretty healthy response. Maybe it would seem more polite if American's made like they were embarrassed about the ignorance when it comes up, but that would go against being honest.
My point is that Indians (for example) aren't embarrassed by their ignorance about Brazil (for example), but expect Americans to be embarrassed by their ignorance of India.
Any time spent learning about the details of some other culture/country is time not spent on learning about another. Faced with the abundance of sets of details to learn, and with little to make one country/culture's set of details stand out as the one an American might want to learn, lack of self-recrimination is a pretty healthy response. Maybe it would seem more polite if American's made like they were embarrassed about the ignorance when it comes up, but that would go against being honest.