The Panama Canal was built because the US wanted a way to get from the east to the west without having to go around the tip of South America which was an additional 13,000 miles. At first they tried to convinced Columbia to build it with an offer of $10 million but they refused the price and demanded more. To avoid higher payment the US Navy encouraged Panama's independece and helped them win freedom. As a gesture of thanks, Panama built the canal for free, making them a crossroads of world trade.
The Mexican Revolution was led by Francisco Madero against Porfirio Diaz. Their supporters were split into socialists, liberals, anarchists, populists, and agrarianists. Madero had many important followers such as Pancho Villa and Emiliano Zappata. Pancho Villa was known as the Robin Hood of Mexico because he would often cross the Mexican-American border and steal from the Americans. Emiliano Zappata was famous for his battle cry "tierra y libertad", translated to "land and liberty."
Commodore Matthew C. Perry arrived in Uraga Harbor with the intention of convincing Japan to open their ports for American trade. Japan had every intention of saying no, but the American ships were so much more advanced then their own and upon the threat of a war with no doubt more advanced weaponry they agreed to open two ports to the Americans.
The Opium was fought between the Chinese and the British because the British were secretly smuggling opium into China and selling it to it's people and had managed to get over 12 million Chinese people addicted. The Qing Emperor wrote a letter to Queen Victoria asking her why she would allow the British to distribute opium in China if it was illegal in her own country. When he didn't recieve a reply, the Chinese declared war on the British. But due to their outdated technology, they experienced a crushing defeat.
The Monroe Doctrine was written by US Presiden James Monroe with the intentions of keeping European countries from invading those in Latin America. This proved to be effective in preventing the colonization of the Latin American countries but the Latin Americans grew to hate the United States, referring to them as the "Colossus of the North" because they were a looming power.