It becomes defense in depth though, perimeter defense is no longer enough. Thats kinda new.

https://en.wikipedia.org/wiki/Operation_Spiderweb

I bet you could do aiming and firing in less than 0.1 seconds with nearly 100% accuracy in the 50 meter range which would enable ~10 destroyed drones per unit if the drones are going 150 km/h.

Shotgun pellets are also basically entirely safe when shot into the air as they have low falling velocity enabling usage when shooting over populated areas.

And then all drones tracked by satellite so any drone that doesnt show up gets shot down anywhere over a large geographic area.

Using cheaper drones to hunt down expensive drones.

Or of course, just eagles.

But why go through all that when you can just have someone in the country launch it, or drop it off?

Or this: https://www.epirusinc.com/electronic-warfare if you think the C-RAM would get saturated. Whether the weather balloon drones move at night is irrelevant if you stop the last move they need to make.

Militaries have been defending themselves against attacks for as long as they've been around. Drones will change the way they fight a little, but it isn't going to be some magic pill that modern militaries can't adapt to. Hiding an explosive and then blowing it up when your target is nearby? That's almost the same concept as assassinating someone with a car bomb. Putting it in an Amazon box and letting the drone go the final distance changes things a little, but militaries and governments were able to assassinate people remotely before drones.

Swarming attacks with cheap munitions? Saturating an enemy's defenses has been a thing at least since the time of the English Longbow. The longbow regiments would all shoot at the same time, and while you could dodge one arrow it was hard to dodge all of them.

Drones are new and will take some adapting to. If a military refuses to change then it probably will be disadvantaged. But the US military has been buying and testing drones for a while, and is already undergoing the adaptation. As it better understands cheap drones for offense, it necessarily gains a better understanding of what is needed for defense.

To be clear, I'm not advocating for the US attacking Iran. All I'm saying is that the US military is not about to lose the conflict because of this particular tactic.

Everything else is a half measure.

get real please.

And these are either autonomous drones (more expensive?), or fpv with the fiber optic line out the back - either way you have to get them in range without being detected somehow.

In short, i think this is an unrealistic scenario - fun to imagine as a horror-sci-fi idea but unlikely to be deployed. Just one opinion.