It wouldn't be a "rival", it would be a third competition potentially creating two (Canada and USA) competitive international teams. In terms of number of top level athletes produced, the USA is the world leader, and if they knew about the game and understood the rules, tactics, etc then a team of college football players who didn't make it to the NFL or CFL would probably be better than any international RL side other than Australia.
It's all fanciful and pipe dream stuff, but it wouldn't be a bad thing at all if it actually somehow happened.