What product will insulate an exterior PVC pipe coming out of the ground with a faucet on it?
You need a "frost-proof hydrant" (which will have a garden hose thread, not a fire hose thread.)

That is a valve that is buried below frost line. On the hose side of the valve, there is a small, deliberate leak (this should not leak when the valve is open.) When the valve is closed, the leak drains water from the standing part of the pipe.

Without heat, even a fairly absurd amount of insulation will not prevent a pipe standing in the cold with non-moving water from freezing; so this type of valve removes the standing water.

Here is a picture, from the state of Indiana (they evidently don't want this type to be used due to the subsurface drain.):



Here  (from Simmons, a manufacturer - no affiliation or recommendation implied) is the more complex "sanitary" alternative type with a sealed canister and a Venturi to drain it when water is next used: