Which of the following was a reason some Americans were in support of American Imperialism?

Immigration needed to be restricted

The US needed to maintain their isolation from other countries

The need for natural resources and new markets

The US should not expand beyond its current borders

The correct answer is The need for natural resources and new markets

Imperialism is the idea that the United States actually should expand beyond its borders, which it did when it went westwards or when it took the Philippines. Being isolated is also against the idea of imperialism, while immigration is not as related to the idea. The only thing here is the need for resources and new markets which is a part of imperialism.