Question

How did the crash of the u.s stock market affect germany and other European countries?

Answer 1

It sent their economies into further decline--European countries had invested in our stock market and they relied on our financial assistance following the war. 

Germany was relying on circular loans from the US which provided funds to help them pay for reparations. After the stock market crash, we were no longer able to aid which stopped money from flowing into Europe. This caused further decline in Europe preventing them from investing in their own countries let along buy goods from the US.