Overseas vapers buy largely from local and Chinese vendors.
So they already have access to product with reasonable shipping costs. It would not be worth buying from the USA unless they need a hard-to-find item that local vendors don't have, and there's not enough of a market for that to keep a business profitable/viable.
Also, because of TPD, it would be illegal to import or export non-TPD products so few, if any, will take those risks seeing how those buyers have access to those products already, with reasonable shipping rates.