I’m more familiar with the Civil War than the WWI recovery and the WWII recovery but I’d like to point out that there were two massive factors to the WWII recovery plan which were kind of opposite lesions from the Civil War.

With the Civil War, there was a lot of destruction requiring repair. There were massive social and economic transformations required as part of the ending of slavery. Those were drivers to encourage investment. On the flip side of the coin, much of the South remained in active rebellion via the KKK and in lynching blacks and maintaining white power. Many Northerners did not share President Lincoln’s and Johnson’s general sense of forgiveness and these Northerners wanted to punish the South. The federal government needed to occupy the South for a while to ensure the peace and protect the blacks. The South wanted the North out and eventually got their way. In hindsight, a lot was lost with social progress but at least the South remained loyal and peaceful, at least towards the whites. America didn’t spend a ton of money on recovery and it worked more or less fine.

WWI came and finished and the punishments placed on Germany were severe. Germany couldn’t recover and add in the Great Depression and the economic disaster lead straight to WWII.

So, there was a massive lesson there. You don’t destroy the conquered economy. Help it recover.

The second massive concern was Communism. The world saw what it did to the wealthy leadership in Russia. The end of WWII was obviously the start of the Cold War with Russia. America needed strong allies. So, the biggest well known stated reason for plans like the Marshal Plan to help the Western countries recover were to build strong economies that would align with America against communism. So, again it was in America’s interest to dump in a ton of money into friendly economy’s to help them grow and encourage a strong western economy.

So, I just scratch my head to think of major ties to the Civil War as America seemed to get away with something (I.e. underinvestment and abandonment) that clearly didn’t work after WWI.