Possibly because it turns out the woman who played that role in the original series was… well, let’s just say her Native American ancestry has been “disputed” (and her character was supposed to be Native American).
And the reason Kayce is a Navy SEAL is… because that was his backstory in the original series as well? I know plenty of Navy types from landlocked states or, failing that, landlocked areas of states (eg: west Texas is as landlocked as New Mexico, Oklahoma, or Montana, but of course Texas has a substantial coastline… 800 or so miles away).
Eh… not that long. The Navy allows people to enlist with a BUD/S contract. We’re talking a standard 4-8 year enlistment contract.