For teas try Twinings. For a wider range Forntum and Mason.
They both had US distributors when we were last there.
We obtained Stilton easily. Certainly in the main cities, especially on the east coast, there should be little difficulty.
You can get a butcher to provide suet as there is little demand for it in the USA, or else Atora is available from some places.
Good liquor stores in major US cities will stock British ales and ciders.