High speed rail is a non-starter in the US, except for in certain regions. It's 2000 miles from Chicago to LA. Optimistically, if you had a train that averaged 200 miles an hour, it would still take 10 hours. That's just not competitive.
Security lines are shorter, and the beginning and end of a train trip both happen at a literal train station, so it's usually easier to get into and out of the city center.