Answer:
1. The US helped other countries after World War II and couldn't go back to being isolated.
2. Truman wanted to help countries fight communism, which was good but also had some bad consequences. .
3. It is hard to say which is more successful in fighting communism because they both have their strengths and weaknesses. Economic aid can help countries rebuild and become more stable, but it can also be hard to measure how effective it is.