Listen, according to the law, under the Magna Carta act revised in 1961 in New York, Seeds are not considered to be illegal and therefore not considered contraban in international shipping.
HOWEVER, the patriot act, that was recently renewed, makes it easier for them to know that you are ordering seeds, if they have a reason to watch you. I will say that like much Marijuana legislation, it's legal in one way, illegal in another.
Take this into consideration. When you buy seeds from Europe, you get them in packs of ten. Unless you are buying some insane amount, very little attention should be brought to you. Ultimately, it isn't against any federal law to buy seeds, and it is not against a federal law to smoke Marijuana. It IS a federal law to buy, sell, or distribute or have on you should someone look in your pockets. If you want to buy seeds in a State that completely bans Marijuana, at some point, you should study the particular laws, becuase it sounds like you plan to break it. I don't know what your goal is...just grow pot for you and your friends, or become a kingpin of your local refer world.
They probably won't track your card, but if you feel nervous, do what bloodshot says and take precautions...any of those Mailbox Inc places are cheap for a mailbox, and they aren't double checking your ID when you sign up for one. Order seeds over the mail with someone else's name. Just do a bit of internet research on the companies before you send out your money order across the globe...you don't want to send two hundred bucks to some fly-by-night scam in the Netherlands that you will never see again because of your fear of a paper trail.
Or just do what I did, move to a legal state, get your papers, and co-op with other growers...