How did winston churchill's "iron curtain" speech impact the truman doctrine? the speech convinced americans that the ussr was an enemy, rather than an ally, which led to the creation of the truman doctrine. the speech made americans aware that the ussr had nuclear weapons, which led to the end of the truman doctrine. the speech showed that great britain was not strong enough to oppose the ussr, which led to the rejection of the truman doctrine. the speech revealed that eastern european countries were no threat to their neighbors, which led to the creation of the truman doctrine.