No, you're making a very confused argument based on extrapolating from your premise that Uber is better than taxis in the suburbs (undoubtedly true), to the conclusion that Uber can replace personal cars in the suburbs (highly unlikely). Yes, Uber is better than cabs in the suburbs. But hardly anyone takes cabs in the suburbs. The only people who don't own cars in the suburbs are people who can't afford them and have to rely on the bus.
Your example about forgoing a second car totally misses the mark. Families have multiple cars in the suburbs for one of three reasons: 1) householders need them to commute; 2) stay at home spouses need them for school drop-offs and errands; and 3) teenagers need them to go to school, friends' houses, and after school activities.
Uber is not a practical replacement for any of these core functions. The average commute in Metro Atlanta is 17.5 miles and 30 minutes, or $30 each way on Uber X. A stay at home spouse will generally make shorter trips, but more of them. Two trips per weekday to pick up/drop off kids at school, and potentially several more for errands and after-school activities. Moreover, most of these will be multi-hop: drop the kids at school then drive to the pharmacy to pick up a prescription, then drive to the Costco to get groceries, then drive to Giant to get stuff you don't need to buy in bulk, etc. Teenagers with cars will take several trips per day as well, to/from school and to after-school activities.
There's a reason that the U.S. has almost as many personal autos as people old enough to drive them. In most of the U.S. you can't even leave the house without driving, and unless you only leave the house once every other day to go to a place within 10 miles (which is nothing in terms of suburban distances), you'll spend vastly more on Uber than on a personal auto.