The factors that caused the Great Depression to spread around the world are:
Americans stopped buying from overseas nations
Many countries raised tariffs on imported goods
Americans demanded repayment of European loans
The Great Depression was the worst economic downturn in the history of the industrialized world, protracting from 1929 to 1939. It began following the crash of the stock market of October 1929, which sent Wall Street into a panic and wiped out millions of investors.
Prior the Great Depression, the Federal Reserve had caused banks to decrease their willingness to loan money to the people. the stock market also declined at the time before