Affiliate Marketing Secrets

Hi,
I will be traveling to the U.S from Canada. To do a 4 month internship with a reputable company. However, I will not be recieving school credit, or pay for my participation. Im confused as to what visa, if any I need to obtain.
Ive been told by some I dont need any since Im not affiliated with a school, nor will i need a green card because im not getting paid. And since its under 6 months I should be ok to fly over, do the internship and return without further documentation.
Can someone provide me with some clarification or knowledge on what i should do? or if you know the visa type… than that would be even more helpful .
Thank you.

Ok so last month I applied to several internships for the summer…b/c I was desperate and many of the due dates to apply had past….so I applied to like 7 of them. One of them contacted me…but its one of the one’s that I really didn’t want to do because I would be working for a different political party that I am affiliated with. But I really need an internship for the summer…so idk- is this ethically ok to do?

I’m having a difficult time figuring out what I’m good at. I’ve taken some strengths quizzes and they seem to give me a decent idea, but they are also somewhat general and if you know what the Barnum Effect is that’s probably playing somewhat of a role in taking those quizzes too.
I’m a 20 year-old college student so I should really start to figure this out as I need to start applying for internships and what not soon. I may also be a bit modest, so that could also be making this difficult. But I mostly think I just haven’t found the right niche. I do have a job right now, but I wouldn’t say it emphasizes or brings out my strengths as much as it does for other co-workers.
Where should I start in this investigation?