If your reasoning was correct, it'd still be wrong because then you could just cut the missile in half
But no, if the beam diameter was small, the missile/plane would just wear shades and complain about the bright light, because the increase in spot size due to divergence.
Yes, but to take down a drone you need a missile. And missiles are extremely - EXTREMELY - expensive. Something like 50000 dollars apiece, or more. This costs one dollar to fire. Much much cheaper.
This. Plus, point defense projectile technology has been lagging over the decades, and while current kinetic kill systems like Phalanx have classified ranges there's a lot of rumbling they aren't up to task. Not the mention the environmental issues of firing a few thousand rounds of tungsten or depleted uranium tipped ammo.
The laser systems basically heat up a small area on the target, and the air frame obviously can't dissipate the heat so it catches on fire.
This might also discourage Russian bombers from pointing their targeting lasers at American ships. Just point yours back and flash it a few times to get the message across. A lot of flexibility here.
Might be possible to mount version in an AC-130 as well.