I'd spend extra money that would have gone towards war on building houses and schools in less fortunate countries. Housing would be free or extremely cheap in those countries because everyone deserves a roof over their head and an education, if not more. I would do the same things for those living in poverty in the U.S.
I know Americans may not like this idea, but I would increase taxes to help fund medical research. Hopefully, the extra money could lead to cures for diseases like cancer and HIV.
Last but not least, I would require everyone to take a life skills class covering subjects like getting a job, paying taxes, legal systems, sex education, social skills, childcare and cooking. It would almost be like a home economics class mixed with business enterprise. Hopefully, this would help young Americans from graduating high school and then encountering what comes next.