Getting a working visa in the US is abit of a nightmare. You can stay there for 3 months on a holiday visa but you are not allowed to work leagally in those 3 months. To qualify for a working visa you need a solid job offer. The company who has offered you the job then has to apply for your visa not you and this could take anything up to 3/4 months. The way to get round it is to get a 'sponsorship' from a company, it's basically abit like work experience except they pay you your proper wage, it's just a way of getting round the red tape, alot of companies do it. It's not illegal or anything just abit of a shortcut.