There are indeed Americans who have a very restricted world view. However, there are also Americans who are well-traveled or at least well-read and who have a sense of how people in other countries think and live.
And, to be honest, I could say the same of almost any other country. There are always people who for one reason or another basically know and understand only the folks in their immediate village. I say this as an American from Texas who traveled to London only to discover many people otherwise intelligent who basically believed Texas is the same thing as Dallas and honestly wanted to know if I had met J.R. Ewing (this was a few years ago).
Sometimes parochialism is unsurprising. For example, my family was invited to dinner by a Guajiro family while we were visiting the jungle near Angel Falls. The reason was because they had never seen people that looked like us and they were curious if we could eat the same foods and understand basic human ideas. The answer was yes, although only my father ate the rhinoceros beetle grubs. He told the man of the house through several interpreters that he couldn’t allow his women to eat them. The gentleman agreed and commented “I know what you mean. Once you let them have something good they demand it all the time.”
In other words, I think any country contains citizens who cannot understand how others live, and hence are surprised both when they turn out to have the same values or very different values as themselves.
It is just that there are so many of us Americans, and we tend to be so loud.