Since Tasmania.Aus started growing a major legal cash-crop of opium poppies (legal opiates have to come from somewhere), garden poppy seeds are no longer easily available in our shops. The USA does not like to buy legal opium from countries that have illegal opium, and as a result we have zero political tolerance for edge cases.
Also, I’ve read that American florists (like Aus) no longer use poppies, or poppy seed cases, and that restriction dates, I think, from the late 20th century, not from the earlier disputes. I’ve looked, but can’t find any references.