I agree, these games need to be played. But, for the most part, they won't be. The only reason England is playing in this tournament is because Australia and New Zealand aren't playing this year. Would England travel to Canada or the United States to play a game against the lesser opposition that would be supplied? Would they travel to Lebanon? Would the Kangaroos or Kiwis travel to play lesser opposition such as this? Not bloody likely? So these games, "that have to be played" to make the lesser nations better, are not likely going to be played anyways. And even if they were - they will still shed a poor light on the sport when there are better ways to bring the sport to new fans around the world.
International RL is not a joke, it's just the nature of the sport, there is nowhere to hide and no spoiling tactics that can be employed like in other sports. Wales had about 4 players today that would be classed as regular first graders, the rest were either talented juniors or players from lower competitions. If you pit full-time professional players against semi-pros and kids, then the score is always going to be a blowout. Full-time against amateurs, in the case of USA or Canada as you have suggested, would just be a waste of everyone's time and potentially dangerous because of the nature of the sport. Canada lost by 60 to a team of English amateurs FFS.
The aim is to get Wales, France and the other 'tier 2' nations to the stage where they are able to field entire teams of full-time players. France are almost there, Wales should be in a few years, the others may take a little longer but ultimately that is the way to ensure a competitive international scene.
As for your idea about 'showcasing the sport', the interest in watching two foreign club sides playing would be absolutely minimal compared to watching the national team playing, regardless of the standard, and if we don't follow up with development from the ground up then the whole thing is pointless anyway. In the case of nations like the USA, Canada and Lebanon, we're talking about countries that have been playing the sport for a fraction of the time of the big 3, clearly there is no easy way for these nations to reach the level of those that have been playing for 100+ years but that doesn't mean we should give up or not bother trying, there are no quick fixes, it's just a long, hard road that these nations need to take in order to reach the level where they might be able to compete. It could be 50 years before Canada can realistically take on even a team like France and be expected to be competitive, but if that's how long it takes then so be it.
We shouldn't be afraid of blowout scores, they are inevitable given the nature of RL. If you think the sport at international level is a 'joke' then wait for the World Cup next year, where pretty much every team will be comprised of professional players.