It can be argued that US involvement in European politics could have prevented another world war. Support for the League of Nations could have stabilized the region. The US government did not support the League of Nations and without the US supporting it quickly crumbled. So because of American absence in the continent due to isolationist policy, it can be argued that World War 2 was destined to happen because of the unfair Treaty of Versailles
Farming was a source of income in the colonies
Russia and Britain both gained partial control of Persia's economy.
Slavery ended when President Abraham Lincoln delivered his iconic Emancipation Proclamation. This would eventually free black people so they could become ordinary citizens and NOT slaves. So basically, slavery was ended all thanks to good ol' Lincoln :)
