What’s the fastest train in the USA?

AcelaAmtrak's Acela, which reaches 150 mph (240 km/h) over 49.9 mi (80.3 km) of track and Brightline, which runs at 125 mph (201 km/h) in a dedicated ROW between Orlando and Cocoa, are the US's only high-speed rail services.

Why does the U.S. not have bullet trains?