The Great Depression was a worldwide catastrophe because the economic recession spread around the world and impacted many people in a variety of ways. The deep recession in the United States in Europe increased unemployment and resulted in deep economic turmoil. This spread around the world leaving economies weaker, trade weaker, and social well-being worse off.
The idea that a proletarian revolution is needed is a cornerstone of Marxism; Marxists believe that the workers of the world must unite and free themselves from capitalist oppression to create a world run by and for the working class.
The US believed that they should focus on themselves more and less on the world, and to not meddle with other countries affairs, and so they pursued a policy of isolationism
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