I sell to Europe and Canada, seller ID "gramps", I have to fill out a customs declaration form, no big deal really.
Last year shipping to Canada was $9.50, and shipping to Europe was $13.50.
Shipping to anyone in the US was $2.45
Two years before that I could ship anywhere for less than $4, closer to $3.
I offer unlimited wins with shipping as long as it is all shipped to same address on the same day, I figure that high win volume should get a postal bonus besides extra bonus seed.
I also tell the buyers they need to know if their country has laws on importation of seeds, it would be pretty hard to keep up on every country's laws regarding seed importation.
I have never had a problem shipping to Canada, a few problems of non delivered, to both Europe and the United States
So I do not guarantee delivery outside of the US anymore, but I keep all postal receipts because I do guarantee that I shipped and can prove it if need be.
Shipping seeds from Europe to the United States, last year a new shipping law took effect, I'm not going into details here but the hoops put in place to get seeds from Europe would make it not worth the effort for the vast majority of seed buyers.
I would stop offering seeds to Europe if the same laws were passed in the US.