Who's to say that the Confederacy would've been the body to abstain from WWI or WWII? Maybe the Confederacy would've been the half of America that fought on the allied side of the war, and the Union would've not involved itself at all. Afterall, England and France were very, very close to openly allying themselves with the Confederacy during the Civil war. Perhaps if the Confederacy had become an independent nation, they would've been very closely allied with Europe. Europe and the Union were both more industrial than the south, and they both needed agricultural goods and things like Cotton that the south grew, so maybe the Confederacy would've boycotted the Union and simply traded all it's goods with Europe, and thus become close allys with European nations. Simmilarly, the Union would have been in direct competition with Europe, and maybe the Union would have been particularly opposed to helping out European nations.
If the Confederacy had been the last hope during WWII, would they have been able to pull through?
It's true that Russia didn't have lots of help in winning their front of the war in terms of supplies or soldiers being sent there. However, if there weren't such strong fighting on the allied side on the western front, the Nazi's could have concentrated much more on the eastern front and possibly have changed it all. Imagine if the USA had never involved itself in WWII and Britain had fallen to the Nazi's in 41 or 42. The Soviets definately did not have their front of the war wrapped up by 41 or 42, and it would have been totally different if the Nazi's were only fighting a one front war.