问题：
What made the United States a powerful country by
答案：
During the two World Wars, America remained neutral in the early stage. However, Americans continued their profitable trade with the warring countries. Therefore, they not only retained their military forces, but also accumulated great wealth. When America entered the wars, it was almost at the end of the wars. By sharing the fruit of victory with other allies, America greatly strengthened its power and became a powerful country by the end of World War II.