If Russia was 'invading' our southern border trying to claim Texas, New Mexico and Arizona their 'property' based upon some fantasy then I would see your argument (kinda), but what NATO (and you correctly stated that The US is bearing the majority of the bill) is doing is preventing Putin from occupying a sovereign nation, thereby (hopefully) showing enough power/will to prevent any further hostile take-overs on other neighboring countries. It's no secret why Sweden and Norway hastily applied to be a part of NATO...the writing is clearly written.invasion of their southern border and see their President deny there is any problem on the border.
For context, what The US has provided in aid/ammo/artillery is barely 3% of our military budget (basically a rounding error in accounting), and for that small amount we don't have any American lives at risk on the battle field. The Afghanistan debacle was roughly $300 million PER DAY! I'd say the amount we're providing to help Ukraine is cheap national security insurance.
Now for the argument that Biden has been 'asleep at the wheel', I'd counter with the alternative of where we'd be if the incompetent coup attempt was actually successful.






