Why did American isolation grow after WWI?

Explanation:

... RESULT The USA became isolated from other countries both economically (trade) and politically (by staying out of the affairs of other countries.)

There was an increasing fear of foreign people after WW1. This was due to the war, but mainly the fear that they would take American jobs (because they accepted lower wages.) ... RESULT The USA became isolated from other countries both economically (trade) and politically (by staying out of the affairs of other countries.)8 May 2007

then its a law the end

the answer is a) to be able to obey them.