We must have very different definitions of "covered". Looking at the supercharger map on Tesla's website, I'm not sure that even the SoCal area is close to fitting that definition. Most east coast state have only 5-10 stations for the entire state. Unless Tesla is planning to increase the rate of supercharger installations at an exponential rate, it will probably be another decade before the US will be covered to the point that you could reasonably expect to take off on a long distance trip without needing to plan around charger availability.