The Great Depression started in America but it did not stay there. It found its way to other countries and affected the world as a whole. Here is a short summary of how the Great Depression found its way 3,000 miles across the sea from America to Europe to affect other major countries of the time.
After World War 1 Europe was in bad shape. The war had left the continent dismantled and in debt. To help out the U.S. passed the Dawes Plan which allowed U.S. investors to start lending money to the major countries in Europe to help them recover and pay their debts.
This worked out fine until 1929 when the stock market crashed in the U.S. As a result many of the investors in the U.S. wanted their money back, the European countries who were still under a lot of financial stress found themselves in an even deeper hole then they were before and suddenly found themselves up a creek without a paddle.
So began the Great Depression in Europe something that would last all the way until WW2.