What this graph tells me is that the US will likely be quite good at rugby quite soon. They have a large and growing player pool, good retention rates and with more and more attention being paid to the dangers of American football there are going to be a lot of kids shunted towards rugby as the less brutal of contact sports. They have a pro comp starting in a few years, or so I'm told, which can only help. They also have a potentially powerful development network in the NCAA (college sports).
While the last thing I want is America to be good at yet another sport, I can't help but think this would be good for rugby... Right?
Absolutely fantastic for rugby. With growth in the American market comes the possibility of tapping the wealth of TV rights. Unlike the Australian market, people here in the US are willing to pay for TV, and the money in it is huge. To break that market though, the sport needs to become much larger than it is now. Remember that the population of the US is approx 300 million, and 80,000 players is like a drop in the bucket.
It is interesting that you said that rugby would be considered the less brutal of the NFL and Rugby. I can tell you that that is not the widely held view. Yanks consider rugby players to be brutes because they do not wear padding or armor. I don't know how many times I have heard that comment, and while I don't have any hard facts to dismiss them with, I do what I can to reassure them that it is not a game where players can indiscriminately harm others.
What is true though, is that are masses of players that did not make the cut either at HS level, or at College level. In football (ie gridiron) there is no other outlet for these players to continue at club level or socially. the vast majority of players become spectators in HS or college, and a great number have potential to be good rugby players. I have heard that a number of programs try to convert these players to the heaven's game, and are quite successful at it.
It is only a matter of time. I cannot tell you the number of people (different group of people to the 'rugby is brutish' lot I mentioned above), who love the game. Their usual comment is about how free flowing the game is, unlike the stop/start nature of NFL that begins to bore people.