Fact is, the US was a late adopter to more modern drones, or UAVs, having fallen behind countries like Israel and South Africa who had developed propeller-driven surveillance UAVs and used them operationally in combat from the late 1970s.
Both gained much experience in the use of drones to evade surface to air missiles and developed stealth prototypes, including the South African Flowchart, and began early work on weaponising them. As a result, both Israel and South Africa were early exporters of drones, selling to dozens of countries and remaining major sellers. When the US needed to acquire tactical UAVs in the 1980s, it acquired Israeli Tadira Mastiffs. It wasn't until nearly a decade later that the first Predator flew, in 1994.
Both the above countries have armed drones for sale, though refuse to publicise their sales. So even if the US were to scale back its drone research massively, it would not do anything to slow down this pace of development elsewhere, which has only increased with more countries and companies building drones and their subsystems.
It was only in 2001 that trials were first carried out to arm Predators with Hellfire missiles. Not because they were more effective weapons platforms than manned aircraft, but because the idea was to shorten the time needed between spotting a target on the UAV's cameras and hitting it with a bomb or missile.
As such, most countries don't actually need armed drones. They're slower and more vulnerable than manned combat aircraft, are not designed to dash to target areas quickly and are typically more expensive to operate than aircraft like the Embraer Super Tucano or Aerosud AHRLAC because they need more ground equipment and a ground control station. The market for surveillance drones, especially those that can provide some level of persistent surveillance, is huge and growing bigger. The number of countries specifically requesting armed drones, however, remains low.