Taxis in Panama are also more or less unregulated. The cars are barely serviceable, the rates vary wildly, especially if the driver doesn't like your skin color, and congestion is so bad that if you want to get across town during rush hour, the driver will not even bother to pick you up.

Markets optimize for cost. The point at which they will begin to correct for congestion is well after the point of total gridlock (since it costs the driver very little to sit in traffic). You can't drive down fuel costs, so any cost savings have to come from driver salaries and vehicle maintenance. Hopefully the Uber app provides sufficient feedbacks to correct for the market's tendency to drive down those costs, but I tend to doubt it. There is no particularly effective way to provide disincentives for gridlock as far as I'm aware, beyond limiting the number of vehicles allowed on the road. Some countries do this for all personal vehicles already, which may work better than a medallion system, but I doubt it would be popular in the USA.

Same with telco. Markets that were unregulated ended up having the cheapest phone and internet service (and, surprisingly, also the best).