It’s a question about balance. The US historically was far more powerful than in game. It wouldn’t be balanced to give them army focuses especially tank ones. But I do believe they should have a significant land doctrines research bonus as their doctrine was superb for the entire war, just not tank research.Of course, what did the US army do besides fight a two front war and define military doctrine in the West for the next century? :^)
As to the rest of your post, I really don’t see how this tree is an improvement at all to the current tree. There’s no clear historical path (its blended with the bleeding communist path for some reason) and the ahistorical options are a bit bland for my taste. Additionally, the Congress mechanic is going to make PP a very sparse resource for any aspiring US player.