The only way RL will be a major sport in America in 20 years time is if numerous people with many millions of pounds invest in the sport. And I mean MANY people. USA is huge and has four HUGE sports in Grid Iron, Baseball, Basketball and Ice Hockey. Even soccer with it's many billions worldwide is struggling to make a dent.
If RL became a niche sport in USA in 20 years with a few fully professional clubs I'd be very very happy. But you have more chance of winning the lottery than RL has in breaking into the big four (or even taking over MLS).
You can try your hardest to develop the game there, and I applaud anyone that gives it a go. If you have no money, all you can do is offer your services to try and bring in investment and sponsorship to develop players, coaches, etc. And in all fairness, that is a huge achievement in itself which is why I don't see why people keep trying to grab the brass ring from day one as all it inevitably does is disappoints everyone when it doesn't happen. I know I've used this simile earlier, but it literally is like buying lottery tickets for years and being disappointed that you don't win the jackpot.
I'm not sure what attitude you are alluding to other than realism? I've toured Malta and France the last couple of years with my club to play and referee games. I've had a tremendous time doing it, and I would love nothing more than the game to grow in these places. But to believe that SL is an option in 10 years time in Malta (ranked 20th in the world) would be a pipe dream and anyone involved there would agree. In fact, I'd be very surprised if a team from the area we played in France (Nantes) is anywhere near the top league in France, let alone in SL.
That doesn't mean it won't happen. But that doesn't mean I won't win the EuroMillions tomorrow either. I'm simply putting things into perspective as people clearly are talking without any actual knowledge of what is going on or what it takes to run a SL club.