A) Those countries are committed to vertical sprawl. The US srawls horizontally. The utility falls considerably in that setup.

B) We would have to exchange airports with trainports - megastructures that go out to other cities. This, unlike airports, would mean huge swathes of land stolen from the property owners to have a high speed rail line.

C) The distances that make it work in Europe are small. NYC to Chicago is farther that London to Berlin.

D) We already have hugely subsidized passenger rail from major city to major city. Its not heavily used.