Well, EV with a good range still costs more then a plugin hybrid with a small battery. Why US government should spent money on technology that is presently inferior to plugin hybrids? In few years this will change when the latest battery technology will be scaled up, but then EV will be able to compete against ICE or hybrids cars on its own without subsidies.

And in retrospect subsidizing EV by governments around the world could be a bad decision. If instead fuel taxes were raised or at least the subsidies went to development of more economical cars, then total CO2 emissions could be lower at this point.