Not good. Need competition to keep prices affordable and also encourage continued development of infrastructure and services.

There are three large mobile providers in the USA. But there are also smaller regional mobile providers in different regions. There are also providers who don't own any infrastructure of their own, but rent the infrastructure of the big three and sell service at a discount. The service of these resellers is reliable only when there is not peak demand on the infrastructure that they rent. It allows the big three to maximize profit on their infrastructure investment even when that infrastructure is not being fully utilized by their own customers, because they are able to sell the unused bandwidth to the resellers at a discount.