Isolationsim set USA apart from the world troubles hence securing their military, resources, finance (especially since the wall street crash), political scenario, etc. this was both good and bad considering many US citizens hated the TOV as their ancestors were german.
Appeasement's biggest advantage was that it gave time for the allies to rearm. The general public opinion supported disarmament and opposed war. Many british people sympathised with the idea of bringing german speaking people together. However, it gave hitler time to conquer more land and spread fear. It lead to war. It gave hitler time to rearm as well. It revealed that hitler could not be trusted and that all his promises were empty ones. Mainly, it opposed the policy of pacifism that in turn lead to what everybody dreaded- world war.
