We're right back to "remember how big and sparsely populated the US is." 150mph in three hours is good for inter-city transportation in the Northeast, but a lot of other places would have trouble justifying the cost.

And that's nothing compared with what a truly high speed train would cost to implement here.

Again, that's a great reason not to build HSR in Iowa or the Dakotas. But if you look where the population centers of America, this excuse begins to fall down. A huge percentage of America lives on the coasts in fairly dense pockets, far denser than many countries with existing HSR.

High speed rail generally goes a bit faster than 300km/h. At that speed a lot of things are less than 4 hours away. Chicago is a bit less than 4 hours from NYC at that speed, as is Seattle from San Francisco. San Francisco to Seattle is obviously not a great candidate for a high speed rail line because it doesn't pass through much of interest, but it gives a good sense of the scale.