In a strange way, perhaps the world would have been a better place if the USA hadn't joined the League of Nations. At least in terms of international co-operation.
Dissent towards the League of Nations started off strong, and remained strong in America throughout its entire existence. When the World War came, and the League of Nations collapsed, many were glad to see the back of it.
Of course, it was then this antipathy that stopped the Americans from taking part in the talks to establish a new international organisation for the new post-War period, the Soviet Union took control of the process, eventually forming the Global International (Globintern).
Now, I know this may seem like a strange thing for a British citizen to say, but the establishment of the Globintern was a very promising development! It was not, as its critics claimed, an instrument designed to spread global communism, (the USSR had the Comintern for that), the Globintern was strongly modeled on the LoN, with a few very important reforms, (that, in retrospect, probably went to far). Notably, the Globintern's policy of accepting delegations from colonised nations was extremely admirable, but what was ultimately what put it on a collission course with the Imperialist nations, leading to Moseley's (SPIT!) decision to withdraw all co-operation in 1948, and, well, we all know what happened from there...
The Globintern collapsed along with its primary sponsor, the USSR, and nothing has really come to take its place. I mean sure, we have regional co-operation entities, (the European Community, the Organisation of the Americas, the Persian Community, the Nanjing Pact, etc.), but none of these had the overall global scope of the Globintern, or even of the League of Nations for that matter.
And sure, in recent decades its been fashionable to criticise that internationalism as idealistic and unrealistic, its interesting to speculate just what might have happened if the USA hadn't been turned off by the prospect of international co-operation between 1918-38, and had instead took part in the Globintern...