how does the history of europe in the 1930s prove that american great depression was a crisis of american democracy?

The history of Europe in the 1930s shows us how closely connected are economy and politics.

During this period happened what historians call the fall of liberalism. Because of harsh economic crises, poverty, and mass unemployment, many people adhered to authoritarian, dictatorial, and anti-democratic politics. Although this happened mainly in Germany, other European countries experienced similar situations.

For example the only European countries whose democratic political institutions worked without interruptions between 1918 and 1939 were Great Britain, Finland, Irish Free State, Sweden, and Switzerland.

Therefore its explicit the correlation between economic and political crisis. Besides this correlation, it's also important to think about how democracy is failing to anyone who starves, loses a home and doesn't have health or education rights attended to in a period of economic crisis. In this sense democracy and economic crisis are synonymous.