I think you severely underestimate Belgium. They still have a lotta players from their " golden generation " like Lukaku, Kevin De Bruine, tieleman, Courtios, ect. Trossard won the PL and almost the Champions league as an absolute playmaker on front. Generally 4 to 5 topplayers can be enough, look at Croatia back then. Belgium is a dark horse.
having said that two things come to mind; 1. The US showed some really positive football. They clearly making progress as they managed to bully some teams. But 2. Soon as they get some decent opposition, they fold..but the latter goes for more teams like Brazil, The Netherlands, Germany. Even current World champions Argentina almost folded against a much weaker side
I hope some of yall got into football some more, and I hope that more kids will play the game "full time". Because that's what's needed; as kids we used to play full-time football( soccer). After school, on the street, lay down some jackets as a goal and play away. On top of this we were registered at an official team. And from those millions of kids the best of the best got selected for a pro career.
Thats what's needed. The sport n3eds to be ingrained into the heart souls and minds of young boys so the talent pool gets bigger.
Finally, US should try to keep talents in and around the MLS longer and throw serious money at the sport. No more washed up Messi's ect. But fresh prime topplayers. That will be difficult though as Europe simple has the best leagues and it might take decades to build a top league.
It starts with love for the game tho..