The obvious answer is more public transport infrastructure & bike lanes.

If you think population density is an excuse for public transport infrastructure not coping or need for more people owning cars I suggest taking a long hard look at e.g. Japan to have that hypothesis reality-checked.

I'm btw. not saying you did, just reading between the lines.

As I wrote in an earlier reply to parent, NYC hasn't managed to even build ring Metro lines around its city center – since a century!

And that is for one reason and one reason only: not nearly enough (political) pressure from the public to improve public transport infrastructure.

And that in term gets us to the root cause again: the US can't imagine itself without cars.

This is not a critique. It's just an observation that is very plain to see if you grew up in Europe (and possibly many other places, too).

When/if that changes, ever, the above things will just happen naturally.