All three of them have American stations and lots of sports channels. I suggest you contact all three, see their channel line up, get pricing, and decide which is best for you.
I've used both Multivision and ITS myself in the past and I've seen American football on both (although just in passing - I was just flipping channels). I switched to ITS cuz they always get the rights to the soccer cup but I'm not sure which one of them has more American football.
If you find they don't have what you want, get back in touch with me and I'll try to find out more for you.