I think the reality is that Tom isn't, and never was, much better than another American - Scott Moninger. For those of you on the other side of the pond asking "who?" Scott stayed over in the US for most of his career, and won race after race, including both Mt. Evans and Mt. Washington, the Gila and many other small races. He could climb, but had a bit of a kick, sort of like Cunego or Valverde, so he won a lot.
But he never rode the Vuelta, didn't get any big TV airtime. Didn't have anyone say he's the next Lance. He just kept racing stateside on teams like Crest and Mercury, and winning. Tom's top climbing speed is faster than Scott, but Scott was much, much more durable.
The point I'm trying to make is their talent level isn't that different from one another. Only that Scott stayed over here and won more races than anyone ever imagined he would, while Tom got all the hype and couldn't deliver anything more than one disappointment after another.