What effect did john hay’s open door policy letters have on the imperial powers of britain, france, germany, russia, and japan? a. it provoked the imperial powers to declare war on the united states. b. it caused the imperial powers to restrict trade in their trade with china. c. it warned the imperial powers that the united states would soon declare war on china. d. it signaled to those powers that the united states would take a larger role in world affairs than before.