The current Acela rolling stock is already slated for replacement with European-style cars that are lighter and faster. [1] But you're right. For the most part

The current Acela rolling stock is already slated for replacement with European-style cars that are lighter and faster. [1] But you're right. For the most part the bottleneck on Acela speed is the tracks, grade crossings, overhead wires and lower speed passenger traffic, not the trains. [1] https://en.wikipedia.org/wiki/Avelia_Liberty https://en.wikipedia.org/wiki/Avelia_Liberty