Just like guns, why bother smuggling it in? It would be easier to buy/build it within the US. As for deploying it, anyone can drive a pickup to within range of a variety of US bases. These aren't remote arctic outposts surrounded by tundra. US bases are generally near civilian populations. Nobody would think twice about seeing a pickup truck parked near a base at night. Any number of aviation enthusiasts do this regularly.
It doesn't need to be some super-advanced weapon or capability. Sometimes all it takes is a demonstration to make people aware of vulnerabilities that have long existed. Think about the billions spent on airport security after 9/11, that frankly aren't doing much to prevent future attacks. This incident, and others like it, don't have a body count and haven't provoked a massive public outcry, but they are unnerving people. You can bet funding is going to be diverted to securing airbases from this sort of threat.
It probably wouldn't be necessary for someone like China to actually stage a demonstration, since its easier for China to just have some high up diplomat get themselves drunk and boast to or around a known CIA operative that they have hundreds of drones ready to strike facilities in the USA that can be activated on a moments notice. Then leave just enough of a paper trail lying around in other places to validate it (although probably a dozen or less, not a hundred), without compromising anything. Maybe even go so far to have a private military briefing (that a CIA operative was invited to) which displayed a particular model of drone built using off-the-shelf parts that could be acquired in the US ("we built this on our soil, we could be building another one very much like it on your soil").
