I'm American, and you're right that there are a lot of people like that. I have been around a lot of rednecks and they love America because "we're the only free country" and other such ridiculous nonsense.

Even the "realistic" ones still believe some myths like that America saved the world from the Nazis in WWII instead of Russia.

It's hard to say whether they are the majority, but they're a significant portion. And reluctant_commenter is right that the media only focuses on happenings inside the U.S. Just put an unlabeled world map in front of the average American (including me), ask them to label the countries, and watch them embarrass themselves.

We are a really massive and powerful country so there's a lot going on and it's easy for news outlets to focus exclusively on what is going in the U.S., other than very occasionally mentioning something one of our rivals like China or Russia is doing.

I mean, just look at the names of the public broadcasting services in a few English-speaking countries:

Britain: BBC - British Broadcasting Corporation

Canada: CBC - Canadian Broadcasting Corporation

U.S. - PBS - Public Broadcasting Service

And it's really common for Americans to not have traveled "outside their backyards"; they're not some rare breed. It's more common in the ghettos in the cities (and these people tend to hate the U.S., but also tend to hate other countries even more), where some people have never even traveled around the whole city, much less outside it, but this is also a thing for rednecks in small towns who only occasionally go to larger towns for things like malls.