That is because you're only looking at USHL games. They play games against NCAA teams which honestly are more valuable than a lot of OHL games in terms of caliber of competition, playing BU, Michigan, Wisconsin and Minnesota are bigger games. They also play friendly tournaments and several other competitions that are very high value. While yes some also comprise the CHL guys as well especially the summer stuff you have misrepresented the games here pretty badly.
For instance here is his draft year statline from eliteprospects.
Dylan Larkin at eliteprospects.com
So how many games do you think he played that year???
Now if he was on an OHL team that made a deep run he would have played more games. He also has a world class weight room and better strength and conditioning programs than exist in the CHL. While yes those are nice they just don't quite stack up to what a federation can throw at that stuff. The USMNTDP has changed hockey in the United States, it isn't because they have something wrong. While I could never see a world where Canada follows the model as the CHL is too established and wildly successful as a business, to pretend the US model isn't living up is well.... Sorry I don't get it.
Here are Hughes' last two years for another look at this: