Is this a US thing I’m too French to understand?
I’d say likely yes to this. It’s much easier to centrally govern a more geographically dense and homogeneous country.
In the US we have strong localized government (city/county, state) and the more sweeping Federal government.
And they do submit to central government, that’s exactly what the discussion in this article is about- will the central court decide to strike down their local laws?
The actual article is in The Hill
The president can’t just appoint whoever they want. Officer commissions have more oversight than say judicial appointments. They have to be approved by the Senate (eg this situation) and also have to meet requirements for the position/rank set out in regulation by congress. So a president could theoretically only promote the most conservative officers in the pool, but it’s already a small pool.
Even so, as we see here, it only takes one senator to block promotions. This isn’t even a fillibuster, the Senate passes this routine stuff through bulk unanimous consent.
The podcast Ultra by Rachel Maddow goes into the history of this period and is really good
The 14th is a reconstruction amendment btw, it wasn’t drafted or ratified by the founders.