Get hired by an American Airlines wholly owned (WO) regional airline. It's a guaranteed slot towards AA.
Start rushing the ANG units before that. There's a lead time of a year, or longer, from the first interview to SUPT. I'd wait until I've got less than a year to 1500 hrs. That way you can ensure you'll be at an AA WO before you leave for SUPT.
Don't enlist. It's not required.
While you're on active duty (AD) for training your seniority is advancing at the AA WO. You'll come back as a senior FO, or junior CA(need 1000 hrs 121 to upgrade), and will be well on to your way to being qualified for all the majors once you reach 2500-3000 TT.
If you're not flying a lot in college (500 hrs+) I'd recommend quitting college full time once you get 1500 hrs and get a regional job. Finish up the degree part time. If you get on with an AA WO sooner you'll flow to AA sooner. And if getting your degree is delayed 6, 12, or 18 months it won't impact your getting a major airline job. It might delay, slightly, you're going to SUPT. But the difference in going to SUPT at 23, 24, or 25 isn't a factor.