I cannot comprehend the thought of "maybe someday we will need them to ensure our freedom"

Watch Red Dawn (either one, there was a remake recently), if you want it explained in a nice easy fictional movie format I'd say that simplifies it and sums it up as well as it can be.

No country is immune to another country putting troops on the ground no matter how tough we believe any of us are. If Russia, China, or the USA wants to get troops into your country, it can happen. It's typically the deterrence of someone larger coming to their defense or mutual destruction that stops countries from doing it. In our case, it's our own, average person being able to defend themselves that creates the deterrent. But again, watch red dawn.

And private firearms won't do shit against tanks and drones.

Not that I really agree with it, in some states there are private firearms and explosives that are legal that could totally take down a tank or a drone... heck some people OWN private tanks and drones