I think Americans know badly EU so it seems for them that EU is just something big and unclear, kindda one country. But to ask why EU is not USA makes me think a lot, yeah.
Americans are really weird. Why do you expect that EU is one country? It has one currency and some other common things but it is mostly politic thing than real economic. How can you compare England and Germany with Hungary? Do you want to tell they have the same budget or the same president to do the same quality of roads and railwaystations?
So in this case I will complain that I cannot come from Washington to Brasilia, just because this are both Americas.
Try to understand that there are a lot of countries who at first hate even English language just because they hate Americans goverment. Relation to usual Americans is good till the moment they ask ketchup in Italian or French restaurant or their american beer in Germany or Prague…. But I would not expect the same situation as in Germany or France in Poland or Romania.