If you have good pressure from your pump, but not city water, the restriction would be in the short section or fitting s from the city water inlet to where it tees into the main water feed line from the pump before the first fixture. After that point it's common plumbing to the whole RV, pressurized by either or both sources. Check inside your cupboards from where the city water inlet is to where that line connects with the line from the pump, usually fairly close to the pump. Hopefully just a link or pinched PEX line.
Ken
