After WW1 people and the government were afraid another war could happen and thousands of people would be slaughtered.
President Wilson came up with the idea of a league of nations which would be made up of many country's with a Representative from each country and the aim would be to keep peace.
If a country did anything to go against the league they would:
1: be verbally approached
2:Trade stopped with them
3:war
However before the league was finished being done America had to pull out as the government were against it. People in America at that time were in high business and good trade, so businessmen were against the idea in case trade had to stop. Then there were some Americans who were anti-British and French as we had colonies and the Americans were for freedom and so they wouldn't want to help fight for colonies problems. Then there was the problem with soilders being killed.

So in the end the major country's left were Britain, France, Italy, And Japan later on Germany. But none of these country's were financially able to support it, and America was seen as the middle of the bridge; the the main country needed. However it carried on but soon failed when problems began.
1:Japan with Manchuria (the league of nations failed to help with China being attacked by the Japanese)
2:Italy with Abyssinia (failed to stop Italy take over Abyssinia)

And so some of the country's left and the league failed ww2 began.

Do you think it would have been different if America had joined?

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The past is what makes us who we are dont make it your burdern

There would be serious issues with colonies. Europe only began decolonizing properly after the second world war. The LoN consisted of mostly European nations and the few other independent nations (mostly clustered in South America), and would end up being a forum for more Imperial issues.

I dunno would have it changed much if the US would have joined, and stayed. Depends again how much would they(any of the major powers that is) follow the rules (it doesn't seem to working with the new LoN, I mean UN), and would Britain again opt for appeasement rather than confrontation.

Too many if's to make a valid speculation.

PS: The LoN wasn't a complete failure. It did successfully settle quite some border disputes between lesser powers. Finland vs. Sweden over the Åland Islands, and Romania vs. Hungary over border lands.

PPS: You forgot to mention the LoN failed to do anything (besides expel them) when the USSR, unprovoked, attacked and tried to conquer Finland in 1939. They failed but, thanks a lot LoN!

Yeah i suppose your right Britain was more for appeasement and keeping peace and so was France at one point so it does seem it probably still wouldnt have worked. Each country wanted to rebuild thier country and avoid war so stopping trade wouldnt have gone down well for any country and so i suppose it would have failed.

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The past is what makes us who we are dont make it your burdern

When it comes down to it, countries only try to save their own tell, the whole problem is that we can't trust other nations to think in our best interest or for us to think in theirs

One of the main reasons that the LoN failed so badly so often was that either France or Britain wanted to go to war with even the smallest country and neither would go to war without each other. If America had joined there would have been an army capable of upholding the LoN's aims. This, in fact, is one of the reasons the USA did not join, they knew they would be the ones providing most of the men for the fighting force, and they didn't want to be dying for European politics.

I believe that if the USA had joined the LoN would have been far more successful, and although it is unlikely this would have prevented war it may have delayed it and then made it easier for the allies to win.

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"Experience is the ability to recognise a mistake when you make it again."

The US army was not the effective military machine we know today during the inter-war period, I'm not sure how much it would have mattered. Either way, an "isolationist" government would not join it. But a US economic blockade on country X would have been effective, methinks.
The LoN was doomed to fail from the start, nobody really cared about it.

The only reason nobody cared about it and nobody listened to it was that it was ineffective. The only reason it was ineffective was that after The Great War the only country big enough to lead such an organisation was America, Britain and France were well and truly up the creek and they ended up running it with very limited resources. The trading sanctions could never be effective without the number one trading nation in the world - the US - agreeing to uphold them. The military sanctions could never work on the jokingly named military that was left in GB and France, the US was the only superpower that everyone, to some extent, trusted that was left strong enough to head the military operations.

The League of Nations needed the US badly, and I don't think that it would have been ignored and disrespected by it’s members if the US had joined in.

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"Experience is the ability to recognise a mistake when you make it again."

It's true that the U.S. wasn't anywhere near the nation that it became via WWII, but it's also my impression that France was quite defanged and near broke after the Napoleonic wars and was ganged up on by pre-LoN alliances. Depleated going into WWI with scarcely a defensive breath caught by WWII, France was only a shadow of her former self. And it was why a balance of power was in every nation's best interest---mainly where Europe was concerned; if the U.S. felt distanced by what was going on in Europe, it's no surprise. Our only claim to fame were the loansharks we had here speculating on war expenditures Europe had to make.

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To me, I think coalitions are great but no entities that can't do anything to enforce their own laws

France was not at her best, but she still wasn't a pushover. Even most Wehrmacht generals were surprised that France fell so quickly. But yes, a balance of power was in everyone's interest, except the US. The US profited greatly from European conflicts.
Britain and France were strained, but not to the point of collapse. They both managed to hold their colonial possessions up until another global war came along. Still, neither country particularily cared about the LoN, even more because of Great Depression when it struck.
The US was only an economic superpower at the time, not a military one.
Read any book about the mobilization done in 1917, and it will agree with me. The US had pretty much the freedom to do anything it wanted in the Western Hemisphere (as it still does), but outside of the Western Hemisphere were European interests to deal with.
So far, in 1918, the US military record was not too shabby.
- Defeated the British with French aid
- Tied the British, Washington burned
- Destroyed Mexico
- The North fought and annexed the South.
- Annialated various American Indian tribes
- Fought and defeated Spain (), and even then with difficulties
- Helped defeat a worn out Imperial Germany.
- And various police actions in their own "backyard".
Comparing this to the French or British military records does not do the US justice. Anyway, as I said earlier, colonial interests among others would scuttle the League.