I despise anyone who becomes a soldier of their own free will. The moment you enlist, you accept that you will be obliged to kill, and that you will have no control over whether that killing will be justified.

I wonder what would happen if we didn’t have a military at all

We wouldn’t see images like the Iranian girl’s rucksack smeared with blood.

Good point. But let me ask you this:

Without a military or nuclear weapons, what is preventing other countries from taking advantage at the first chance they get?

Criticize the U.S. all you want. But the country is full of valuable resources that other countries want. Take away the U.S.'s ability to defend themselves and the risk of foreign nations taking advantage will spike dramatically. Nukes are basically the ultimate “don’t even think about it” sign.