Honestly it's not worth the risk trying to get them past U.S. customs
I thought about doing exactly the same thing when I was last in Amsterdam..
I realised I would be stressing out the whole flight home- and border security are trained to spot anxious body language...plus they only have to look at your passport to see where you've been and put two and two together-believe me-you don't want to get interrogated and shaken down for a bunch of seeds..
Its just so easy to buy them online these days-or by all means arrange while you are there to have a [reputable] dutch seedbank mail them to you.
JMO..
..Good luck, whatever you decide to do mate.