Only two things I can think of, a pressure regulator on the spigot that is clogged, or a clog somewhere IN the hose. Do you have an inline filter? Try a new hose, and try a new spigot.
OMG-I just looked at your Airstream model and year. If the Airstream is new to you, there are TWO water inlets one on top of the other. The top one is actually the sprayer that cleans the black tank, the bottom one is for city water, but both may be labeled fresh water only. The bottom one has a better cap on it.
Today is a gift, that's why they call it the present.