If the airplane isn't in the clouds and is below 18,000 feet MSL the pilots are still responsible for seeing and avoiding other traffic. There are a lot of places in the USA that don't have ATC radar coverage, so traffic separation is based almost entirely on see-and-avoid and cloud distance laws for VFR pilots.

The ATC problem is probably the easiest one to solve, and there are already some solutions in use like D-ATIS and automated pre-departure clearance (PDC).