Not sure when it became gospel that once u beat the crap out of a country u have to build them back up. Almost seems a good strategy to start a war with the US and loose it so they will build u up out of your 3rd world status. Japan and Germany did pretty well for themselves after getting rebuilt after WWII. Vietnam still pretty much a crap hole. Likely the biggest mistake they ever made was not giving the US a win then standing around with their hands out. We should have just gone in, taken out Saddam, made sure they didn't have WMD and then got the heck out IMO. Germany and Japan had more for us to work with than Iraq and Afghanistan, would be hard enough to build the last two into anything, assuming they really wanted to be anything other than a fundamentalist backwater. Trying to drag them kicking and screaming where a good share of their population doesn't want to go, not likely to work out real well. And not our call to decide for them what sort of govt/economy etc they should have. Let them make their own choices and sink or swim on their own.
The purpose of war is to kill people and break things. Armies not really the best agent to be a meals on wheels program. Once the troops do the job they are best at, bring them home till u need someone smacked around again. Foreign troops on someone elses soil usually not real welcome unless they invited u in. Sticking around after the shooting is over not likely to make them love u any more.