Non-interventionism: A policy of not interfering in the affairs of other nations—like choosing not to take sides when two friend groups have a fight at school.
Monroe Doctrine: A U.S. policy which opposed European colonialism in the Americas while also avoiding involvement in European wars—it's like telling others not to bring their fights into your backyard, while also staying out of theirs.
Neutrality Acts: Laws passed by the U.S. aimed at keeping the country out of future wars—like making a rule for yourself that no matter what happens, you won't get involved in any schoolyard fights.