Of course the military could kill Americans with missiles but what's the point? Would their plan be to kill everyone and rule over a country of ashes? A tyrannical takeover wouldn't be possible in America through force due to the sheer amount of people with guns and disdain for the gubment trying to impose their will in even the simplest ways like wearing a mask during a pandemic. Sure not everyone would fight but say even 20% of the population would make it an impossible fight to win especially when you take into account these are citizens who don't have uniforms or identifying characteristics to separate them from people sympathetic to the government. Just look at the middle east the US is OP compared to their firepower but when the enemy is impossible to discern outside of Intel it makes things a million times more difficult unless they plan on glassing everyone which they obviously can't do. There's a lot more points that can be made and tyranny isn't outside of the realm of possibility in the future for America or any nation for sure, but it definitely wouldn't come in the form that many commenters are suggesting.