I live in the United States :) I think that it is easier to learn English in an environment where everyone is speaking English and you're surrounded by English signs and such. As for culture, I think it really depends on which part of the country you choose to visit :)

If you intend to study in USA, for a full time student. it's a good choice. base on you can afford the cost of living, school. if you are oversea student or international student. a lot of schools and training accept you. If you want to study and work together, you need to balance your time. you would be very hardship and perverse it. and you get the visa into US. Even I moved to US for 6 years. I can't freely speak with native. because a lot of words, sounds not recognize. because I need to work at the same time. Learning English success or not depends on different people. I knew some people like a girl from brazil. she learn very fast. she joined local dancing Kung Fu every week I forgot the name she told. depends on different one. A lot of opportunities help non native to speak English. library, church, community. college. Here from Boston. I have a friend who open a business to help chinese go abroad, if you are interested, you can ask me. :)

I have only been to the US as a tourist so I can only tell you about my impressions - people are very friendly and warm but they can be a bit fake. Regarding English, it depends on your native language but it is not a very complex language I believe. It is all about exposure! Try and listen to English music!