What are some causes and effects of the U. S. overseas expansion?

There were five major things that caused the U. S. Overseas Expansion:

1) New Manifest Destiny: the mission to reach from coast to coast

2) Commercial Expansion: the need for new interactions in international markets

3) Naval Power: this was still during the time when naval power was one of the greatest military powers a nation had. Having more of it, ensured your success in conflicts and influence

4) Darwinism/"White Man’s Burden": Christian/Catholic missionaries’ missions to "uncivilized" nation, such as the ones in Africa

5) Closing of the Frontier: Americans wanted to have the "frontier", or unmapped regions mapped and explored

All of these resulted in the spread of democracy, American influence and the realization that America was a big player at the table of nations.