During Reconstruction who took over Southern state governments? Why would this be troubling to Republicans in Congress (think)?

The Great Depression was mainly an American depression back then America wasn’t as centralized as it is now so Germany was hardly effected by it now they where affected by the after affects of ww1 that’s what’s actually gave the nazi regime the call to arms to take over the country after there “ unfair treatment “ after ww1 and there want for revenge