It wouldn’t make a dent. Defense as a whole makes up ~$750 billion out of $5.8 Trillion in expenditures.
Of that $290B goes to normal Ops and maintenance of existing equipment and infrastructure, and $170B goes to personnel. $170B goes to RDT&E which actually does expand out into regular life all the time (hello internet and GPS).
The $136B in procurement is what most people think the rest of the budget goes to. This is the defense contractors building overpriced things the government buys. The F35s, Raytheon missiles, multi billion dollar aircraft carriers, etc.
The mandatory expenditures are the big ticket items though, with a combined $4.1 Trillion.
Health care is the biggest one weighing things down. Medicare, Medicaid, and the ACA tax credits cost a combined $1.442 Trillion a year.
Social security is another big one at $1.213 Trillion.
Moving to a universal healthcare system, and eliminating the social security tax cap (currently any income over like $150k is not taxed for social security), would do a TON to actually cut costs and raise revenues.
Raising the cap on social security taxes should be a no brainer, especially if you raise the floor for it too, should be a no brainer. Exempt then first 10k in income and eliminate the cap and social security would be funded forever while the working class would also see a significant tax cut.