Causes in the USA:

The Effects of the Depression in the USA on Europe

Recall & refusal to renew short term loans
The collapse of the German economy
The system of international debts and reparation payments collapsed
There had been an outflow of gold towards the USA / the Great depression magnified this unhealthy tendency
Shrinkage in world trade
Prices fell due to lack of demand / rapid rise in unemployment
Social problems led to a rise in political extremism
Led to the development of Economic Nationalism (promote recovery in ones own country at the expense of others)

Isolationist policies of the USA who imposed heavy import duties which led to retaliation from European states
Keynes promoted Gov. intervention and this tended to result in economic nationalism
USSR was the only one not to experience the effects of the depression and this led to a belief in tight state control as the way of the future.
Failure to keep international agreements
The rise of fascism which was highly nationalistic

Short term benefits to some countries, i.e G.B and German, but it is doubtful that there could have been long term benefits, but the outbreak of WW2 totally changed the economic scene
Caused a further contraction of the volume of world trade (imposed imposition of tariff barriers)
Contributed to deterioration in international relations
Promoted Gov. intervention/management of the economy
In the long term, world leaders came to recognize the importance of economic cooperation and institutions such as the IMF and the World Bank were established.