The thing about America is that it is NOT a single culture. We're an incredibly mixed culture with much variation.
If you said that America was crap, yes, a fair number of Americans would get pissy about it, but equally many would agree with you completely.
The difference in culture between the ultra conservative Texas, the nanny-stateist California and New York, the meth-dealing Tenessee, and the other states...It's like lumping France in with Latvia as far as culture goes. Sure, they're both European and share a "similar" history, but the similarities stop there.
Even the laws among states are very different, and the education system in some states REALLY pushes patriotism while other states don't at all.
So, in conclusion, yes, I would say that it's a bit of an unfair stereotype. Although, simple patriotism isn't the same as having an aneurism over making fun of the US. I have "pride" in what the US *used* to stand for, the *concept* of rights that the US says it supports yet doesn't. But I digress...