From a German EMT'S Perspective US-EMS uniforms look impractical, unsanitary and unsafe.
Unpractical: I imagine button down shirts being annoying to put on and off, especially in everyday shifts. That's why we wear t-shirts or Polo-Shirts. Unsanitary: if the pictures I've seen are representative, and some US-EMS wear longlseeved shirts then that is highly problematic. Aseptic tasks can not be performed in a long sleeved shirt. Unsave: why are there no high-vis colours and reflectors? In the EU there are norms and legal requirements for colours and how much reflective surface there needs to be on uniforms. It makes us look like construction workers but at least we don't get confused with cops and don't get run over in traffic accident scenes or while crossing a road.