Final answer:
The United States became isolationist before and after WWI due to the fear of economic recession, the desire to avoid future wars, and the lack of military power.
Step-by-step explanation:
The United States became isolationist before and after WWI for several reasons. One reason was the fear of another economic recession. Many Americans had suffered from the Great Depression, and they were hesitant to engage in foreign trade and investments that could potentially lead to another economic crisis. Additionally, there was a strong desire to avoid future wars.
The devastating loss of lives and resources during WWI made many Americans reluctant to get involved in international conflicts. Lastly, there was opposition to globalization and a lack of military power. The United States did not have a strong standing military after WWI, and some Americans believed that focusing internally and avoiding foreign entanglements would be in the country's best interest.