To play US discs you need a DVD player and TV capable of displaying NTSC. AFAIK, all DVD players and probably all modern TVs are capable of this.
Most adult DVDs are region free so you won't need a multi-region DVD player.
However, you are still got guaranteed perfect results. For example, in my experience recent Pioneer DVD players (from the last two or three years) don't get on well with RGB playback of NTSC discs - not a problem, however, unless you prefer RGB to S-video.
Never knew that. Luckily I've never had any of those problems with my newish Pioneer, as I wouldn't accept anything less than RGB.
BTW, marzalek, the TV doesn't have to be NTSC compatible. As long as you use RGB signals, it just needs to be 60Hz capable. By far most (but not quite all) TVs less than 10 years old are. In PlayStation forums it's usually referred to as PAL60.
If your TV can't handle 60Hz, many DVD players (check your manual) can convert to 50Hz, but the results I've seen have IMHO not been acceptable.
I have a Pioneer 646 and get a weird bleeding effect on my Panasonic TV - had the same problem with a 545. A friend has a bang up to date Pioneer with a four year old Sony TV and same problem, whereas I don't think we had the same problem with the 646 which I tried on his TV when I bought it.
Personally, I find S-video to be acceptable and in some respects prefer it to RGB.