What if the drone were so inexpensive and portable that you could consider it like you do ammunition? Then the flight time and payload is much less critical - it's just a pilot-able bomb.

This is called a guided missile, or a loitering munition, depending mostly on how quickly it gets to the target. They’ve been around for a while and are very useful but have not rendered tanks obsolete yet.

What if we just donated that money to all these hostile countries' citizens, and told them we'd stop the donations if they piss us off? Instead of dreaming of turning the future warzone from Terminator 2 into a reality?

Well, that (economic intervention) has effectively happened to Russia. And yet they are still going it seems. So to answer your question: Nothing would happen, at least for a few months it seems.

It's easier for infantry to carry one drone and ammunitions than a set of one-shot drones.

In practice it’s actually the opposite. A reusable drone has to have enough fuel to come back, which halves its range compared to a loitering munition that doesn’t come back. A reusable drone isn’t intended to collide with the target, and can’t be rocket-powered, so it will be much slower to reach and strike a target when the target is identified. It has to have the ability to land and to be rearmed, which adds complexity and thus expense.

Past a certain size a drone can fly high enough and far enough that it fills the combat role of an aircraft, but as far as man-portable systems go, well-resourced militaries demonstrate consistent preference for single-use guided explosives like the Javelin or Switchblade to maximize range and payload size and minimize time to impact.

https://en.m.wikipedia.org/wiki/AeroVironment_Switchblade

https://en.m.wikipedia.org/wiki/FGM-148_Javelin