I agree that the US military is huge and expensive, but that doesn't address 'military need,' which is a question of which missions are worth funding and what the requirements are for each.

If your goals are just coastal defense and prevention of invasion from Canada and Mexico, then that's significantly easier. Those aren't the US goals and haven't been for a long time. And it seems to be overwhelmingly the case that any potential defense partner for the US (aligned interests, not judged to be themselves a threat) can successfully pass off military spending to the US.