There were several different factors that caused the US to become a part of the imperialist movement, including:
1) Industrialization- The invention of technologies that allowed for the mass production of goods allowed businesses to make more of their products than ever before. Due to their increased ability to make large sums of goods, these individuals wanted the US to expand their global influence so that they may have new consumers to sell their products too.
2) Social Darwinism- This idea revolves around the concept of the "survival of the fittest." Many Americans felt that the US was a superior society that should spread its ideas and influence in order to help less civilized countries/territories.
B.
The US never declared war on Germany because of the Poland invasion. Britain and France declared war on Germany because of the Poland invasion.
The United States was having the most problems with Japan, and the US declared war on Japan shortly after they bombed Pearl Harbor.
Once the US declared war on Japan, Germany declared war on the US due to the Tripartite Pact.
Answer:
The answer is option 4, Caesar Augustus.
The Mexican-American war came from America taking Texas. Then that allowed us to receive even more land, more than 500,000.