quote: In the US we already have an electrified corridor (DC-Boston). However the problem isn't the speed of the trains: it's the congestion on the rails. The high-speed Acela spends most of its trip between DC-NYC well-below its top speed due to the rail congestion.
quote: The shinkansen lines are completely separate from other tracks although they often use the same right-of-way. In the Northeast corridor you will have the Acela, the Metroliners, regional rail, and freight running on the same rails and often at the same time. Again, the problem is not the quality of the rails, it's the congestion. The Acela, which can operate at well over 80 MPH often pokes along at less than 40 waiting for signals to change and other trains to free up the blocks.