I am 22 years old Swedish citizen, I know that I can visit USA and stay there for 6 months or so without any problems but what are my chances of getting the green card through working or studying over there?
Low, very low. I entered on an H3 visa (interpraktik), and there was immense pressure from the government to stick to that. Any hint of attempting to change the visa status would have been grounds to bar me from entering the country. I got married which landed me a work permit, but the "green card," or permanent residency, was a different matter altogether.
There is the professional sponsorship method (H1B), but then the employer has to prove to the INS that you're uniquely qualified and will not simply fill a position that could be filled by a US resident. Understandably, that's not a realistic option for average dudes.
Skicka ett PM om du vill fa mer direkt information, frugan ar ratt bra pa immigration lagar och bestammelser.