strong enough to prevent anyone from invading the united states, sure. but much weaker than our current military.
If preventing an invasion of the US is the objective you could cut way more than half.
What current military objectives couldn't be fulfilled if we cut the budget in half?
people that know way more about this stuff than i do think it would be pretty touch and go if we became involved in a war with china with the military as is, so i think it's fair to say that if we cut spending in half that we'd be in much worse shape on that front.
by the same token, we are running into hard limits on being able to send aid to ukraine without going below the levels of munitions (and in some cases weapons systems) we consider acceptable for our own use. so, again, seems pretty clear that cutting everything in half would make those limitations even more severe.
honestly, cutting the budget in half isn't even close to a realistic debate. you aren't doing that without violating treaty obligations, diplomatic promises, firing millions of people that signed up with the promise of a steady govt job, health care and pension, etc.
