California is also like this for the most part. Bay Area has 8 m, Los Angeles area has 17 m, and San Diego area has 3 m. 28 out of 39 live in those three. Straight line.
You can see the effect of this here: https://www.chronotrains.com/en/station/2964574-Dublin?maxTi...
I'd assume that similar will happen with California HSR (which would be a far better service than either of the Dublin intercities above); it would make living in intermediate stops and working in LA or SF far more practical.