You can go with larger nodes and larger power budgets for avionics and other electronic stuff in battlefield machines.

OTOH you'd rather be top-notch in your communication equipment, low-power sensors for reconnaissance, etc. In some areas, having a US-controlled 7 nm fab may matter even for DoD.

I personally expect those plans to be dropped or cut back relatively soon as Trump leaves office. I don't think the 2024 date for this plan was at all a coincidence. Taiwan is extremely shifty about their semiconductor tech leaving the island. Of course, 5nm would be very outdated by then either way.