You are looking only at our official entry into the war but our loans and ammunition supply while we were "neutral" had a big effect on the war efforts and policy aims of all the combatants and the eventual outcome. So the vast right wing conspiracy is not wrong about how our intervention made one giant bloody expensive mess out of the whole century.
I wouldn't go that far. We had a lot of help from other less than perfect nations.
Are you sure you're not talking about World War Two?
In WWI, even if we had provided ammo and loans the Czar (we didn't, BTW), it obviously did nothing to prevent Russia's military collapse and the ascension of the Communists.
And you need to explain why a little prevention in the mid-30s would not have been preferable to the need to spend thousands of lives in the 40s.