I work for Gorilla Seeds - one of the site sponsors.
We've just started shipping to the US - you can check us out at Cannabis Seeds | World Wide Delivery | Free Seeds | 10% Cheaper.

From what I hear, if your seeds are detected in customs, they will be confiscated & you'll get a form letter - no one shows up at your door or anything.

Let me know if you have any other questions. As I don't work for US customs, I can only tell you what I know from reading other experiences as well as what I've experienced myself. I spend a lot of time in the US & I've had personal seed shipments come through without issue several times.