'The League of Nations failed principally because the USA was not a member'. To what extent do you agree with this statement?

10 mark answer"The League of Nations failed for several reasons: the USA was not a member; its most powerful members, Britain and France, were motivated by self-interest; and any decision taken had to be unanimously agreed upon. It was therefore unable to take swift and decisive action during crises such as the Manchuria crisis and the Abyssinia crisis. Although the absence of the isolationist USA seriously weakened the League's international clout, this was not the most important reason why the League failed and it was only a contributing factor. The two most important factors were the need for a unanimous decision - which meant that the League could not react quickly to international crises like Manchuria - and the self-interest of Britain and France. Ultimately, it was this last factor that was the most significant in causing the League to fail. The unanimous vote made the League slow and likely to fail, but it was the self-interested actions of Britain and France that prompted them to vote against the interests of the international community, which ultimately led to the crises that caused the League to fail."A clear line of argument, a developed explanation of the named factors and a clinching argument at the end that is NOT simply regurgitating your previous points.