Oh if we're talking about metro area population, then the EU route is also significantly higher (for example, Paris goes from 2 million to 13 million). I was just looking at city limits in both cases.
Honestly I agree with your sentiment. We should connect all these urban areas with passenger rail. But I don't think that this is the first step. Most American cities have atrocious public transit, which needs to be fixed first. No one will take a train from Chicago to Minneapolis if they just have to rent a car once they get there anyway. It would be a shame to invest billions in connecting cities with high speed rail, only to have low ridership because it still doesn't compete with flying/driving.