Well, I wrote a semi-lengthy response to your question and then promptly lost it in the nether world as I hit the wrong key! So, here, in abbreviated form, is my reply.
Rugby is not just for Brits anymore. Although Americans have known about rugby for some time, the game saw a resurgence in the 1950s when US soldiers came back after WWII and, when their own children got old enough to learn, those vets taught it to them. In the 70's, as those same "kids" grew up and had children of their own, many still enjoyed the testosterone-laden, "he-man", just for guys type sport and shared it with their own kids. Of course Viet Nam got in the way and much of the interest faded. But, by the late 80s and early 90s, rugby saw yet another renaissance in America in schools as well as community leagues. Going to work the next day with a black eye, sprained ankle, or a broken finger became a badge of honor! (One of my favorite bumper stickers has always been, "Give blood. Play rugby."
) That 1990s resurgence resulted in professional leagues which, as you have already discovered, miltongs, are even making a mark in Europe. I even recently heard a commentator mis-use rugby terminology in describing a fight in a hockey game as a scrum. I had to laugh but, at least he knew the sport (or so I am assuming).
As to your initial question... If there is more to your story than just the sport, if it's got a good plot line and the story is interesting enough to hold the readers interest, now might be just the right time for it. Go ahead. Get it out there. All you need it the right agent and enough faith in yourself and your writing.
You never know what can happen if you believe in yourself! good luck