The immediate cause of World War I that made the aforementioned items come into play (alliances, imperialism, militarism, nationalism) was the assassination of Archduke Franz Ferdinand of Austria-Hungary. In June 1914, a Serbian-nationalist terrorist group called the Black Hand sent groups to assassinate the Archduke.
During the American Revolution, American society was divided between two groups. One group wanted to revolt against the British and become independent. Another group, known as loyalists, wanted to remain under the control of Great Britain.
With this in mind, it is easy to understand the fact that a loyalist would try to sabotage any efforts by the American colonists to break free from Great Britain. Along with this, loyalists would share inside information with the British military so that they would be aware of the rebels plans.
Because the British government was taxing them heavily.
The Europeans in the Caribbean felt the need to bring in enslaved Africans as laborers because the native American Indian workers had become physically weak due to diseases and the Caribbean plantations were in requirement of stronger labor force. The Africans by birth were very strong and they as slaves would perfectly suit the needs of the Caribbean plantations.
