It's not the pressure, which is probably close to what you have at home (40-50 psi) in most areas of the USA. Rather, you are suffering from a shortage of water volume, i.e. gallons per minute. Most RVs have small tubing for water lines and numerous fittings (angles, tees, check valves, etc) as well, which further reduces flow rates. Then there is your pressure regulator, if you have one (or more than one, as is often the case). Most RV water pressure regulators have low max flow rates, typically 2 gpm or even less.
If you have one of those little brass or plastic regulators from an RV store, it is surely a low flow model. Consider replacing it with a "whole house" regulator from a hardware store. That may not help, though, if your RV has a built-in regulator (many do nowadays) that also has a low flow rate. As for the tubing size, it is often not practical to do much about it, though in some rigs it may be possible to pull new, larger tubing through the raceways, behind cabinets are whatever.