The incidents you noted, 20,000 'bonus army' veterans protesting their mistreatment and the internment of around 120,000 people of Japanese descent on the west coast during the Second World War are not comparable to the proposed fantasy situation in either scope or mission.
As a veteran of the US military I know the law states that the US military can’t be used against US citizens for law enforcement purposes. Congress would have to change the law and good luck with a split congress changing the law. YMMV.
What would they do against three million p!ssed off patriots fighting in their own AO.