That seems backwards. Dense cities are where mass transit is a viable alternative to cars. It would make more sense to focus on that in cities and focus on self-driving cars where individual cars are unfortunately a requirement, like the suburbs.
(Ideally we would Upzone All The Things and the vast majority of Americans would live in places dense enough for cars to be unnecessary, but making NIMBYs stop NIMBYing is harder than just making better tech.)
Car culture is so engrained in the US suburbs that people will insist that they need to keep driving themselves. You see it if you ever bring up bicycling or god-forbid walking.
Cities are the only place where alternative transportation is somewhat normalized in the United States.
(Ideally we would Upzone All The Things and the vast majority of Americans would live in places dense enough for cars to be unnecessary, but making NIMBYs stop NIMBYing is harder than just making better tech.)