US Customs will send you a seizure letter when they confiscate illegal contraband. The letter will tell you how to contest their seizure and who to contact to do so.

Some times your addy will be flagged, but it is impossible for customs and/or USPS to watch the whole nation. Just not enough manpower.

If you repeatively get seizures sent to the same addy, they will eventually come and get you.

The wise thing to do is get a new mailing addy and use it. International purchasing is now risky business.