If both are available to you, then no matter how crowded the roads will be, a car that drives you directly from A to B will be the better UX than a bus that drives you from somewhere near A to somewhere near B via C, D, E and F.

So the car could only be the worse experience if it is hard to get one (Because all the cars near you are occupied by other people) while a bus is easy to get into (Because there is one near you and you still fit in).

The vast majority of worldwide rides will continue to be done in individual cars. The extremely crowded situation that would make a bus the better experience is extremely rare. Most rides worldwide are definitely not done in that kind of environment. And the removal of parking spaces and the better routing self-driving cars allow will move even those environments more towards the individual car.