People need to educate themselves, WW2 was not a consequence of Versailles, but a consequence of a long held German desire to dominate Europe, the same as the cause of WW1. Many many Germans supported the thought that Germany should expand it's European and World empire to control more territory, they saw it as their right as they had such a large economy and large military.
If we compare Versailles with Brest-litovsk a treaty between the Germans and Soviets in 1918 then we see what a harsh treaty looks like. If we look at the way the Germans were dealt with in 1945 then we see a harsh settlement. Yet Germany has not tried to overturn this last one to return to their previous borders, why because they knew they had been beaten, their shattered cities and enemy occupation confirmed this to them killing German militarism. The trouble with Versailles was that it was a compromise, neither harsh enough or gentle enough to build peace (the latter being very unlikely considering the cost of defeating Germany). Also the issue of reparations is not as big as it seems, the first time reparations were included in a treaty between the newly formed German Empire and third French republic at the end of the Franco-Prussian war of 1872. Reparations were a German Idea so what right have they to feel quite so hard done by when they are used against them?
France would never have accepted peace without a return of Alsace and Loraine, Britain would not have accepted anything less than the surrender of the German fleet. The trouble was all the countries had their own objectives and these differences meant each of the victors were not happy with the treaty as they felt others had put things in there they didn't want.
Even if the US had not got involved in WW1 I think the allies could have won, US man power was in fact of very limited use in obtaining the victory in 1918. With the collapse of Russia the Germans would almost have certainly tried an offensive in the west in 1918, maybe not with the same desperation that they did however. Once this had been beaten, and it would have been beaten, the allies would have counter attacked. In these circumstances the allies would have still been able to drive the exhausted German's back, though it may have been slower and taken more lives (if the Germans had not lost as many in their spring offensives). By 1918 Germany's economy was in tatters and not able to support the war effort as effectively as the allies, aided by America's productive capacity whether they were involved or not. So Germany would have lost, just maybe not as quickly.
Your premise about Russia is flawed, the Germans would have used Lenin to destabilize the Russians regardless of US involvement. And Russia was and is it seems destined to remain under the hands of absolutists and dictators, it seems to work for the Russian psyche.
The only things that could have stopped WW2 would have been these. No depression, without this Hitler would never have come to power as he couldn't get enough support. A proper imposition of the terms of Versailles, had Britain, France and the US actually agreed on Versailles and decided to enforce it's parts together then Germany would not have been able to get in the position she was in 1939, however the political will was not there from the start as many felt the treaty didn't suit their needs. The final reason WW2 could have been avoided would have been if the war had gone on into 1919, Germans did not see quite how badly beaten their army was in 1918 and this lead to the thought that they did not actually loose the war.