Some USA kids my son's age and younger are doing over 6 fig by age 21, but that still leaves a lot of road ahead.
A few others could, but don't want to move to Europe.
As I often point out/remind USA had the best juniors in the world in 2015 (won UCI Nation's Cup). The talent is absolutely there, the desire is not, and I understand why. IT is one thing being a kid and having everyone else pay for it as you miss school in the USA and a whole other thing moving to Europe and making it a life.
It was traveling and racing in Europe that made my kid say he wanted no part of it (unfortunately for him, he let that information out way too early). USAC had a lot to do with it, but bad news early is good news.