can a 17 year old minor travel internationally to visit their freinds and come back?

I know you can do it nationally, but I am not sure about internationally. I would say no.

Well you can if you are British and have your own passport.

If you were under 16, some destinations may require a letter of authority if you are not accompanied by both legal guardians.

I'm pretty sure the US allows 17 year olds to leave the country unaccompanied.