Discontent with the war led to the Bolshevik Revolution of 1917, causing Russia to withdraw from the war earlier and (through the Soviet victory) to become a socialist country with Marxist principles. Socialist control of the state would spur Russian economic growth.
The Ottoman Empire was formally dissolved into a variety of smaller Arab states, which were finally out of Turkish rules. In "freeing" them, Britain made conflicting promises to both Jews and Palestinians about who got to keep a strip of land both groups considered holy, thus starting the Israel-Palestine conflict that still persists over who's the rightful occupier,
Powers like Russia and the Austro-Hungarian Empire ceded some of their land to new states, governed by ethnic or cultural groups that had been previously subdued by the larger government. This principle was called "national self-determination", or the ability for a people to govern themselves— but, of course, it seemed not to apply to colonies...
The indebted state of most Great Powers represented a decline in exports and global economy for the United States. This, coupled with a stock market crash in 1929, kickstarted the Great Depression— an economic recession in the United States that would make unemployment soar. As a response, FDR launched the New Deal for the government to help the average American.
Before, Latin America had relied largely on imports to fulfill its industrial needs. After WWI, the supply of these imports decreased due to European debt, so dictators and reformist presidents backed a policy of import substitution industrialization, which aimed to industrialize countries to reduce their dependence on foreign imports.
Scandinavian countries did not adopt socialist tendencies flat-out and in the way the Soviet Union was doing; rather, they advocated for a system with more governmental intervention but still maintaining electoral principles. This was called "democratic socialism."