Cars are simply very useful, and the whole public transport system together doesn't offer anything close to it, except for people who live in quite large and dense cities. There are many routes where public transport can, in principle, be faster and easier than a car. But for 'non-standard' trips, cars offer an unmatched flexibility.

So most people will have a car, even if they can do most of their transportation completely fine by other means. And once someone has spend the money to buy a car ( and often paid more than really necessary, to buy a car nicer than absolutely needed), the marginal cost of using it for an extra trip is quite low.

If people think cars are in some way damaging the greater good, and public transport would be preferred, I think it is wise to pinpoint as good as possible how they think they are damaging. If it is the COs, tax the petrol. But if it is the existence of the cars themselves, through the parking lots they need and the roads they demand, then a per kilometer charge in any way won't help. People will still want a car for those trips that are absolutely horrible by public transport.

Congestion tax is another story again. After all, who is hurt by congestion other than the people causing it?  I f there is a rationale for congestion tax, it is to separate the people who need the road and are willing gto pay for it from the rest.