That is context dependent. In Texas traffic outside of the cities isn't that bad and so slow speed trains are much slower than driving. Inside the city of course traffic is a factor, but even then I'd expect in the normal case you get beyond traffic in a short time and then driving is much faster. And of course driving is door to door so you don't have to figure out time to/from the stations, waiting on trains and renting a car (this is Texas - not known for transit though these cities are getting better)
If a train is fast, it's going through uninhabited areas (no stops). The moment you start having relatively frequent stops is when the average speed goes down.
That's not to say we shouldn't have the trains, it's part of the entire transportation package.
The key is you build the transportation framework first, and let the city grow up around it.
The train is the most convenient method of mid distance inter-city travel in the UK because it’s so fast. Nobody’s driving the 4 hours between London and Manchester, Liverpool or Leeds for a business meeting when the train takes 2 hours.
Inter city trains in the UK aren’t running on dedicated high speed lines - they’re Victorian routes, pass through plenty of stops on the way and are generally 2 or 4 tracks.
They do have priority over freight though - which along with incremental upgrades over decades means the trains can run at 125mph for parts of their routes.
