Why did the us stock market crash in 1929 affect other nations

Because the American economy was strengthened by the disaster that caused the First World War in Europe. The United States of America became the main creditor country on the planet. The investments and merchandise of the United States began to dominate the spaces in the European countries.

In mid-1928, US investors restricted the purchase of bonds in Europe, especially German securities, and channeled investment funds to the New York Stock Exchange.

And following the fall of the US stock market in 1929, the problem not only remained in New York, but moved to almost every country in the world as a domino effect.

trade with US decreased and hurt countries who relied on the US for resources.