Did the right thing.
From Australia's perspective, it's a bit more clear cut. We were also on the other side of the world, but we were still very much British then, and England was still reffered by many to be 'home'. We were one of the first nations to declare war, and we sent more troops per capita then any other allied nation-without conscription-to a war that didn't directly affect us. It might seem stupid in a modern context, but the empire came first back then. As a reward, Australia had a 'baptism of fire' so to speak, both on the western front and in the middle east (most notably gallipoli), and we proved ourselves as a nation.
I find the Australian contribution at Versailles rather amusing. Our PM, Billy Hughes, was Welsh, as was the British PM (Lord George). They shouted at eachother in welsh about nobody knows what, because no-one else in the entire palace spoke welsh. Also, he was one of the major opponents of Wilson's internationalism ideas and was probably, after the french, the person who wanted to punish the 'bloody krauts' the most. As a reward, Australia got a colonial empire...Papua
as to the poll question; yes, the US should have been involved. Earlier.