What do you think of people who say America is the best country in the world?

I am not trying to be anti-American. I know they're many worse places to live than america and I am fortunate to be where I am. That being said I don't get calling it the best place in the world. I don't mean people who say it is the only place they would like to live best place to/for them. I mean people who say we are great and every place else is crap. For ex. a one question I read this guy said america is the best at everything, that Canada is a frigid, boring, and poor wasteland and the United Kingdom is full of degenerates even though they admitted to never leaving the country. Why do you think SOME people are like this.