DARPA has been focused on preparing the military to prepare for civil unrest in reaponse to flooding on the Indian subcontinent for a long time. At least that was the rationale.
There are people who still have not gotten over the rioting in U.S. cities in the 1960s.
How do you control 320 million people when troops are not permitted to be deployed within the borders? Maybe deploying them along the borders will do the job? Why is it necessary to exercise control? Isn‘t that what government is about? What do you mean, “provide for the general welfare?” That would be a lot of work. Where’s the fun in that?