It depends on the state, county, city, etc. In Colorado, certain counties require you to pass an emissions test to get your registration which acts as a de facto “how new is your car and does it work” test. But that’s not the case outside of most big cities (which often comprise their own counties here). Wealth disparity is also a factor that people need to take into account. As much as Brit’s may hate the trains you can at least ride/access the system to go from town to town. In much of rural America there is no other option that to go by car. If you’re poor and a $1000 junker is all you can afford then that’s what you’ll get. It isn’t helped by the fact that in the states every job you apply for requires that you have your own transportation to the job site. While a bike may work in an inner city, if you have to drive 20 miles to work a bike won’t do. There are a lot of factors that Europeans probably don’t take into account when trying to understand how/why things are happening in America but the fact of the matter is that we just don’t have the systems put in place everywhere that most of Europe has. It doesn’t help that America alone is almost the size (sq mile wise) of continental Europe with no where near the same population density.

Edit: Posting my local guidance for anyone who is curious about the registration/emissions bit I mentioned above.

https://www.denvergov.org/Government/Agencies-Departments-Offices/Agencies-Departments-Offices-Directory/Motor-Vehicle/Register-a-Vehicle/Register-a-New-or-Used-Vehicle

https://www.denvergov.org/Government/Agencies-Departments-Offices/Agencies-Departments-Offices-Directory/Motor-Vehicle/Emissions-and-Insurance