you could cut the US military budget substantially and it would still be the largest military power in the world and well able to defend itself
it might not longer be able to be the "undisputed global power" but, as someone who has lived abroad most of my life and seen American foreign policy from the other side, I don't know that's a bad thing
Although it is worth noting that the war spending the US does do also doesn't translate into being an undisputed global power. They burned a trillion or few in Afghanistan and I doubt that impressed anyone in particular. They didn't achieve anything. Challengers to the global hegemony multiplied in the aftermath.
If they hadn't wasted the resources they'd just be better off with no downsides.
it might not longer be able to be the "undisputed global power" but, as someone who has lived abroad most of my life and seen American foreign policy from the other side, I don't know that's a bad thing