I didn’t serve, but from what I understand the combat units are disproportionately white, especially as compared to the overall population aged 18-35. I would think this group is also largely from non-urban areas.
In other words, I would think most come from a conservative background that respects things like the Second Amendment. So I would just have a hard time seeing the existing military turn on the population in the service of a tyrant.
The Green Berets, Rangers, SEALs, Force Recon, Para-rescue, etc. are very, very white, IIRC. Don’t have any idea why.