Question

The best time for Americans to import French cheese is when they can

Answer 1

The correct answer would be: the best time for Americans to import French cheese is when they can buy the most euros for US dollars. It is widely known that the American dollar is one of the strongest currencies around the world, nevertheless the euro is stronger than the US dollar, being 0.9 euros to 1 US dollar. But if making a comparison between both currencies, although normally stronger than the US  dollar, the euro is also much more volatile, meaning that its value increases and decreases with much more frequency than the American currency. This is why, if wanting to import french cheese, the Americans should wait for a day in which the euro is not so strong, so that they will be able to buy the most euros for US  dollars, and make a better deal.

Answer 2

The best time for Americans to import French cheese is when they can buy the most euros with US dollars.

I would say this is the case with most trade with the European Union.