Uh...............................................................................................................YEAH!
are you sure that what you see isn't -spores -amanitas -just sending to european nations where fresh mushies are legal(ish)
If you mean spores that your going to grow mushrooms with than no. If you mean already dried mushrooms sent to your place, than don't even think about it.
From what I have heard the mushrooms will not end up showing up if you live in the US. People in the UK can usually get them though.
Yeah you can but most likely you wont. If they find them in the mail they will just take them and send you a letter. They'd have to be able to prove that you payed for them and expected to recieve them, a trouble which they would not bother going through.