Anyone paying attention would have contingency plans.
Navistar recently got screwed by something that they should have seen coming from the government as well. Doesn’t mean they had a plan. See the Maxxforce emissions engine debacle for more info on that.
Further, whether the US company had a contingency plan or not doesn’t matter if the buyer specifies what is to be done as part of the contract and leaves no alternative. Nissan, for starters, is notorious for demanding that stuff heading back to Japan be delivered to the port of Los Angeles so their car carriers can go back in something other than ballast.