What could spark a severe global economic crisis?

Beyond cyclical fluctuations and local crises, there is a risk of a severe global crisis that would affect all countries. We see three possible causes of a severe global economic crisis: A severe financial crisis in China, leading to a fall in activity. It could stem from the presence of very high debt that has financed partly inefficient capital; A loss of reserve currency status for the dollar, which would lead to a drastic recession in the United States ( which would spread to other countries) due to the need for the United States to eliminate its external deficit; A return of inflation and the related rise in nominal and real interest rates, given the very high level of debt, which could result from a change in the functioning of labour markets or from a geopolitical crisis that drove up oil prices sharply.