Why did the conflicts and crises of the first half of the 20th century become global in nature?

Ineed ! 10 more minutes until test is ! will give 15+ points and ! kansas history which is an example of popular sovereignty? a. the fugitive slave law enforces stricter penalties for people who runaways. b. the united states congress passes a bill limiting the slave trade. c. settlers in nebraska vote on whether they wish to make slavery legal. d. an abolitionist exercises free speech by publishing a newspaper.