Could be a huge pool of talent out there - think of the American Football players that don't make to the NFL!
All those high school kids and college kids that play the game across the country, but only 240 odd get selected to play in the NFL each year, and not all of those actually end up on a team - so RL could be the perfect place for them to move into. They won't obviously get the financial benefits that the NFL offers, but if it's the physical/skill side of the game they are interested in, they have some amazing athletes that could fit right in to most positions on an RL field.
In that way, I'm surprised RL has never really hit American shores until now...