What caused US bankers to demand the repayment of loans and US investors to suddenly withdraw their money from Europe?

US bankers demanded the repayment of loans and investors withdrew their money from Europe primarily due to growing concerns about economic instability and the rising risk of default in European countries during the early 1930s. The onset of the Great Depression, coupled with fears of bank failures and political unrest, prompted a flight to safety, leading to capital repatriation. Additionally, the devaluation of currencies and increasing protectionist policies further exacerbated the situation, causing panic among American investors and lenders.