I wasn't born here but I love this country and all of the opportunities it provides. I mean, as much as I disagree with AA (and I don't want an AA discussion) this country does so much in an effort to give everyone an opportunity. I lived in Canada for a couple of years and lived in England for 6 and I much prefer it here.
I still loved the unique aspects about England and Canada but I love the opportunities available to people here. Canada I would think gives people the most opportunities outside of the USA but I still prefer all the educational resources that come with a larger populated country like the USA.
I love the ethnic qualities of other countries that I have lived in and visited and enjoyed my time in all of them but overall I just think this is the best country to live in and raise a family. England is landlocked and cost of living is out of control. Not to mention the way immigration is killing Britain and the healthcare for the elderly sucks there. I definitely want to be here as I head into my old age.
Another thing great about the USA is in England you have tests during your schooling growing up which puts you into different levels of schooling and can have a big role concerning your future career path and what options you have. Here, everyone gets the same schooling until the end of High School and the same opportunities to attend colleges/universities. Starting up your own business is also much easier here.
I have other reasons I prefer it here but they are more personal but may not apply to all. I just think it's important to remember that while it's fun to visit a country and you enjoy the people, the food, the history etc. it is not the same as living and working there. Even then, other countries will provide a great life but personally I believe none better than the USA.