I think many US fields are subsidised. Also the Yanks are much more appreciative of GA whereas here its seen as a rich man's hobby and a nuisance.
Many drones won't require "airfields" as such, however the key point is that, as with everything, the Govt is completely and utterly clueless and can't even see to the end of its nose, and so will continue to kneejerk policy-wise with ill-thought-out schemes and reactionary behaviour that they hope will see it to the end of its 5 years in office. See the current fiasco over Diesel cars for example.