Answer:
What was the result of tensions between the US and Germany?: The US ended its policy of neutrality and entered World War I.
Why did the US restore isolationism after the war?: Congress wanted to return to the Monroe Doctrine.
Step-by-step explanation:
A paraphrased version:
What was the result of tensions between the US and Germany?: The US abandoned its neutrality policy and joined World War I.
Why did the US restore isolationism after the war?: A return to the Monroe Doctrine was wanted by Congress.