If Bitmain has some sense in its business model, they should either re-route their shipments so people aren't taxed unfairly, or they should choose a different country for their warehouse.
Bitmain couldn't care less. It's the buyer's responsibility to look at the additional tariffs and have it weigh in to see if buying miners from them makes sense or not.
If Bitmain would have a warehouse in a foreign country (which costs a lot of money to purchase/build/rent), it would then require them to ship all their miners from China to that country, which will only make these miners more expensive because of the additional cost involved. Business-wise, it makes not much sense for them to do so.
More importantly, most of the mining activity happens outside the US, so large scale miners can purchase from Bitmain and ship to X Y Z country without any problems in most cases.