Congestion is a huge issue.

A single subway train can carry hundreds of people, nearing a thousand.

Now imagine how much road will be required to get a thousand cars to some place. How wide the roads will need to be, how many people need to be displaced to fit it. How loud it's going to be for those who remain.

Parking is an issue.

Now imagine, how much parking you'll need to house a thousand cars. It's a building that does nothing but house cars. You need to clear land, it's going to block views and take up space.

Equity is an issue.

Now think on those people too poor to afford cars. All those opportunities to get ahead will be lost to them due to their inability to get around. The deck was stacked against them already, now they have an additional disadvantage.

Environmental issues are another issue.
Think of the energy needed to repeatedly move a thousand car weights every day for hours. That isn't coming for nowhere, even green energy like solar or wind has up keep and wilderness habitat displaced. It's far better than fossil fuels, but not zero. Also think of all the manufacturing for a thousand cars, the tons of metal needed for the bodies, the tons of rare-earth elements for the batteries and electronics. That is if we do go green and electric, more likely it will be all fossil fuels for a long time.

Oh and that single train carrying a thousand people. Several of those will be going every hour for rush hour.

The USA has a reputation for creating urban hellscapes thanks to its car centric approach. You do not want that for your country.