It's a great sport... but "no".
With American football, baseball, and basketball and all the best athletes going there it cannot succeed.
Soccer has the same issue.
Can you imagine the following U.S. Soccer team with players that started from a young age in the sport:
Forwards: Lebron James (F - Heat), Rob Gronkowski (TE - Patriots),
Wingers: Kobe Bryant (SG - Lakers), Andre Johnson (WR - Texans)
Center Field: Chris Paul (PG - Clippers), Adrian Peterson (RB - Vikings), Arian Foster (RB - Texans)
Defense: Clay Mathews, (LB - Packers), Patrick Willis (LB - 49ers), Justin Tuck (DE - Giants)
Goalie: Dwight Howard (C - Magic)
You could do the same thing for Rugby. The domination would be nuts, but since the U.S.A. has all its best athelets going for higher paying and more U.S. popular sports it would be near impossible to make a breakthrough. Only individual sports like MMA is where you can see a huge growth and that is also because boxing has become so corrupt. I see baseball as having some serious weaknesses due to the slow pace of the game and the aging fan base, but it still is strong.
INEPTOCRACY - A system of government where the least capable to lead are elected by the least capable of producing, and where the members of society least like to sustain themselves or succeed, are rewarded with the goods and services paid for by the confiscated wealth of a diminishing number of producers.