It's very, very possible once your National Guard contract is up & you've gotten your bachelor's degree. Before, not so much. Once the Guard has you they don't usually want to let you go.
US Army OCS might want to be a consideration also. But they get the bulk of their 2nd lieutenants through combination of West Point & ROTC. Marines are much more reliant on OCS. Open to anyone with a degree. In anything. Non-STEM majors are okay. Brawn much more of a consideration than brains. Run fast, get strong. Ooh rah.