Getting hired as a bartender
You can't accept employment in the USA on a tourist visa. A company can't legally hire you unless you are already in possession of a visa that allows you to work here, and you must already have a social security number (taxpayer id). You can't enter on a tourist visa and have it 'converted' - you'd need to leave the country while the visa was in process.
You might be able to get a job working under the table, but getting caught means deportation and a ban from re-entering the USA for you, and some hefty fines for the employer. The only way I could imagine a restaurant or bar doing the visa work on your behalf would be if you were actually partnering (bringing a financial investment) in the venue.
Wish I had better news, but it's tough to get a visa for that kind of job over here.