How long does it take to immigrate to the United States?

How long does it take to immigrate to the United States? I am in need of some guidance. I would like to obtain a visitor visa in order to spend some time in the US to study its pop culture for a thesis paper.

I need to do some research first before I begin actively pursuing an immigration lawyer. But, was wondering if someone could steer me in the right direction?

Thanks in advance for your help.