What were some of the new ideas, philosophies, and conditions that influenced how leaders in the U. S. responded to the situation in the postwar world?

Relations between the Soviet Union and the United States were driven by a complex interplay of ideological, political, and economic factors, which led to shifts between cautious cooperation and often bitter superpower rivalry over the years. The distinct differences in the political systems of the two countries often prevented them from reaching a mutual understanding on key policy issues and even, as in the case of the Cuban missile crisis, brought them to the brink of war.

Explanation:

. political or economical policy that isolates a country from participating in international relationships. it has been suggested that the united states participates in isolationism because of its lack of involvement in particular wars or alliances.

roosevelt believed that in light of the country's recent military successes, it was unnecessary to use force to achieve foreign policy goals, so long as the military could threaten force. this belief, and his strategy of “speaking softly and carrying a big stick,” shaped much of roosevelt's foreign policy.