It doesn't quite work here because of various factors both economical and social.

For start, insurance. Most insurance companies will drop you if they find out your car is participating in car sharing. Then there is the push back and problem you'll deal with the car sharing company and how likely they'll cover damages.

If the renter hits another car, then it's going to be a huge headache for the owner. Let's not forget, they'll also be out of a car for months.

Then there is an issue of cleanliness. It's time consuming and costly to clean a car. Who's paying for that? It only takes one person to cost you hundreds and possibly a whole day of work to clean up a car.

People here in NYC treat most of the city like trash. So I don't expect them to treat someone else's car better.

Overall, it's expensive and not very beneficial to share your car in the US. If you push the risk/cost to the renter, then they won't see the value of renting from a car share. If car share is only slightly lower than car rental with more restrictions/fees, then it's the same situation like with airbnb vs hotel.

If we're talking about something like zip car, right now they cost a fortune to rent for a weekend and are dirty af. You're generally better off doing a car rental. Most of the time, it can easily come out to $300-$400 to rent for a popular weekend.

At one point I've calculated the cost, and as well as other people I know, it's much cheaper (and less headache) to own a car especially once you start factoring in SO/family and if you drive at least once or twice a month.