Not a USUHS grad or a physician (yet) but I do work at a military hospital. Contrary to popular belief, emergency medicine physicians in the military actually suffer pretty serious skill atrophy. In fact, this is one of the biggest complaints of the EM physicians I've worked with during my time in the service. I don't know of a single military treatment facility (MTF) in the DOD that is a Level 1 Trauma Center. I know at our base virtually all of the high acuity patients our EMS picks up end up getting transferred to one of the local hospitals. Both the volume of patients and the acuity are drastically reduced at our hospital relative to a civilian facility.
Lots of churn in the military medicine world right now and it includes some discussion as to how this EM problem might be improved/changed. But honestly, no one from the top down seems to have a good understanding of the way forward and the future is pretty unclear. You can click around on this forum and find more information about all of these issues.
Are you planning to apply to USUHS in the near future or do you still have some time? Are you open to waiting to join the service until after residency?