From what I've heard, nothing. I live in the U.S. too, and I am getting ready to order. Make sure it is a good seed bank, something trusted (search this site for good banks) and you will be all set. The worst I have heard, is that the packages were seized on the way to your home. But most seed banks send the seeds stealthy, and the packaging doesn't say anything about seeds or marijuana. Also, if you are buying a lot of seeds, make sure you order in seperate orders, because if you spend a couple hundred bucks on seeds, and they send it in one big order, and that order gets seized, your fucked lol....and by fucked I mean, you lost your money, not that you will get caught, because I am just going to use one of those $100 gift cards on it, and if i was ever questioned about the payment, I would just deny it, because it wouldn't be in my name =D
Hope this helped
-Ars1n