If Mueller or Rosenstein are fired, there are peaceful protests planned in the US.
If you're in a Republican House district, you have far more power than those of us in a Democrat district: you can actually press towards impeachment with the House member in your district.
Most US protests are largely just venting. This, however, can actually apply pressure at a critical point. If you show up. Please do.
https://www.trumpisnotabovethelaw.org/event/mueller-firing-rapid-response/