American imperialism is when a powerful country, such as the United States, tries to expand its power and influence by controlling or influencing other countries. This can happen in different ways. For example, the US may try to spread its values (like democracy, capitalism and human rights) to other countries. It could also involve political control, such as the US supporting certain leaders in another country. Or the US could promote its economic interests in other countries through trade or investment. American imperialism has been happening for many years and has led to different results in different parts of the world.