Right because it's been the default Canadian path, which is where 100% then 80% then 50 % and now around 40 % players over time come from.
Sure, but if you have less good 19/20 year olds, the quality of play lessens. Just a natural part of it. Backfilling with some more high-end 16 year olds doesn't improve quality of play.
I don't see how this "evens out". 16 year olds are way less physically developed than older players. Even lower ceiling 19/20 year olds will be a lot better than the highest end 16 year olds.
The "loser"... no. Just thinking through everything, good chance the CHL will just have to come to a grips with an ego blow of no longer being atop the amateur hockey pyramid.
Sure yeah they'll have to deal with that ego blow as well.
There are 4X as many CHL teams as there are USHL teams at the end of the day. To the extent the USHL stays lean, there is likely plenty of room for them to be producing high-end NCAA players, particularly domestic players that don't want to move countries while still being minors unless they feel like they are left no choice.
All the USHL really needs to aim for is to say "hey, this is also a viable path towards NCAA, just like it always has been and just like the CHL is. You can still play here, atop the USA Hockey junior pyramid, show out, get NCAA offers from premiere destinations, if you're an American kid, you don't have to move, you can just as easily play in a domestic league and not be disadvantaged from college and eventually pro hockey". It doesn't need to try and be "better" than the CHL. Just like The Finnish Juniors doesn't need to be "better" than Swedish Juniors to still represent a viable path for kids from Finland to be pro hockey players.
It's all just a pathway and stepping stone, it's not a Mini-NHL where players should do everything in their power to secure a spot in the "best" league. If there are multiple pathways to something available, they don't need to play in the "best" league every step of the way, which is largely noise (over zealous parents may think their kid playing for the Don Mills Flyers is participating in the 14 year old Stanley Cup but most everyone there is just going to be a talented beer leaguer one day all the same). To get back to the point, when CHL was the only* (more or less) pathway to the NHL, that's where you had to go. The more pathways that open up, the less imperative it is for players to play in CHL. Of course all else being equal, a Canadian kid would rather play there than United States. The goal for USA Hockey would be to say, if all else being equal, if you are an American kid, you should want to play USHL rather than CHL accordingly.