Tax dollars really don't pay for things in the US Federal Government.
Deficit spending leading to an ever rising debt is the source of continued spending. When Debt/GDP grows, we're spending ever more money that we don't have.
Total Debt:
https://fred.stlouisfed.org/series/GFDEBTN
Total Debt/GDP
You're not wrong, but exorbitant deficit spending has its own dire consequences. (eventually) Not that I am telling you anything you don't already know.
Then why have tax at all?
Answer to that is indeed this is tax expenditure.
Although rounding error compared to the war.