Not really, we have exactly those gasoline prices in Germany and Denmark, and it's actually quite okay.

The poor just take transit or bike.

The problem with the US is that outside of a handful of the biggest cities, transit is extremely lacking and the roads aren't bike-friendly at all. It's very difficult to hold down a job without access to a car, especially low wage jobs like retail that change the schedule around on short notice all the time and are often outside the operating hours of transit. You can also get a used car for around $1000, insurance can be had for $30/month, and gas is cheap so owning a car isn't nearly as expensive as some countries. I still drive a car I bought 5 years ago for $1500, it's over 20 years old now but runs fine.

Even some of the big cities (like LA) have woefully lacking transit and everyone just sits in gridlocked traffic for multiple hours every day.

While everything you wrote may be true, the US still seems to be exceptionally bad by international standards. We have a lot of rural communities here in the UK as well, where people also need private transport because the public alternatives are lacking. But our vehicles are a fraction of the size (and have a fraction of the fuel consumption) of some of the giant monstrosities that seems to be much more common in the US, and so even though our fuel prices are much higher (almost entirely due to higher taxes), people living in rural communities still manage to get around. The same is true across much of Europe.

While running a car may be cheap in financial terms in the US, environmentally and in terms of scarce natural resources it is anything but, and at some point the US is going to have to deal with the social acceptability of one person driving an enormous vehicle for long distances many times per week or within our lifetimes there are going to be serious problems.

The poorest citizens don't own cars.

It does depend on where you live. In US they probably do. In EU countries they probably don't.

But they get their groceries from stores that deliver goods via trucks.

The poorest citizens certainly don't own the most extravagant of all luxury items, homes near (decent) transit.

A metro's most car-dependent are its working poor, who need to live the furthest away from the downtown core to afford housing.

Actually they are the only one owning them because they need them

They live outside the cities where housing is more affordable but there's no public transport

The end result would be the same, they would just pass the costs to the consumer.

There is a solution: https://en.wikipedia.org/wiki/Cap_and_dividend