Hi aristo
I haven't ever tried US ferns, and the Fern Expert has only ferned in Costa Rica (superb, apparently).
The Fern Expert grows ostrich fern, cinnamon fern and sensitive fern, but we don't know interrrupted (Osmunda claytonia?) - though we may have seen it at Brantwood in the Lake District last week
There are American Fern societies as well as the British one that the FE is involved with. See:
www.hardyferns.org
(Sue Olsen's site; we have met her on trips)
www.amerfernsoc.org
And the British one is:
www.eBPS.org.uk
There is a cheap(ish) guide to British ferns available from the BPS, so there might be similar publications from the US societies for the US