I disagree, I think that Versailles did cripple Germany. The ridiculous reparation payments, the refusal of Germany to join the League of Nations and a huge blow to its national pride, great unemployment and hyperinflation were also results of the treaty as well. Versailles crippled Germany and it was only as a result of the Nazis coming to power and the policy of appeasement that Germany was able to re-establish itself and become a credible threat once more.

Also the United States wasn't simply isolationist due to the Depression; the United States reverted to its policy of isolationism following the first World War. Economically, there was a system of tariffs in place that meant that it was difficult or expensive to get foreign goods in the United States (many countries responded with similar policies in respect of American goods) and politically the US refused to join the League of Nations, whilst (I believe) placing stricter regulations on immigration. I forget the specifics, but it was something along the lines of the quota for immigrants being set at something like 10% those that were currently already in the US; this meant that it was biased towards people from countries such as the UK, who already had a lot of people living in the US compared to somewhere like - say - Poland that had relatively few.

Also, the outbreak of WWI is difficult to attribute to a single cause. Obviously the alliance system (Triple Entente and Alliance) exacerbated things, as did rearmaments with countries such as the UK vastly improving its navy. There's also the nationalist element that saw Franz Ferdinand assassinated, dragging the Austro-Hungarian Empire and Russia into direct conflict. You can also add into that mix Imperialism in general, gunboat diplomacy (the Agadir Crisis, etc) as well as general political rivalries.