The "Big Three" countries were the United States, Great Britain and Russia. They were called this because they were by far the most important allied players during the war, with Russia and Britain taking on most of the casualties.
The international attitude was the world wanted revenge through a peace treaty and holding Germany accountable for all the damages.
Plessy v. Ferguson- basically Louisiana passed a law saying the black people need it separate car when traveling on train not on the same as a white person.
Plessy was 1/8 African descent (was born free and other 7/8 was of European descent ) and under Louisiana rule he had to sit on a black car. eventually he sat on white only car and got into trouble, just like Rosa Parks. and he was eventually got arrested and tried.
The government created at the Constitutional Convention was similar in respect to the jurisdiction states obtained, branches of government (Judicial, Executive, Legislative). These were put in place to balance one another, they also added the concept of elections to be carried out to select government representatives. Furthermore, the adoption of Naturalization, and the ability to create more states. Hope that helps you...