How did George Kennan's "Long Telegram" and Winston Churchill's "Iron Curtain" speech help to shape US foreign policy during the Cold War?
Both of the things that you mention helped to shape American foreign policy at the very beginning of the Cold War. They both helped to push the US towards more of an anti-Soviet posture.
After World War II, it was not completely clear that conflict between the US and USSR would arise. They had been allies during the war, of course, and it was possible that they could have remained at least somewhat friendly. But both of the things you mention pushed the US away from any sort of friendship. Both of them warned of the bad intentions of the Soviets and the need to be firm and hostile with them. These arguments were convincing to US policymakers and American foreign policy took a hard anti-Soviet line.