Population density is misleading. Vast majority live in urban and suburban areas. Urban areas can handle things just fine without cars (and really they need to stop catering to car transit, remove highways that go through downtowns, and eliminate parking options), suburbs just need to have zoning fixed so there are things like convenience stores or a local doctors office in your neighborhood. If you live in a rural area and want to drive a car everywhere that's perfectly fine, but we need to move away from focusing on what a small percentage of people do and focus on serving most people instead.
Suburbanites will certainly oppose this as well, but eventually economic physics will force them to change their habits regardless of what they want.
> We can barely maintain our existing infrastructure in too many cases, let alone rebuild it all.
Right, which is why doubling down on cars is bananas. We already can't afford to maintain all of these roads, let alone build new ones or expand. Fortunately, there is a lot of low-hanging fruit. Repurposing existing highways to initially allow for bus rapid transit alongside personal automobile transit, for example, can help. We probably need a nationwide moratorium on new road construction for 20-50 years to really get things back in a good state.