Yes, I do think a more severe, longer, and thorough Reconstruction was necessary to extirpate the pernicious influence of Slave Power in the South. In postwar Germany and Japan, the US was willing to station soldiers long-term as well as dictate the new structures of government and even institute socioeconomic reforms such as land redistribution and seizure of assets. Similarly, the federal government should have imposed a new order in the South by immediately crushing any sort of terror movements like the KKK, redistributing land from plantation owners to freedmen as well as poor whites (thus giving the latter a stake in the Reconstruction order while weakening the political, economic, and social influence of the planter class), and possibly even restricting the most egregious Confederates from holding political office. The Treaty of Versailles after World War I failed because the reactionary Prussian Junker class continued to exist and though mostly not Nazi themselves, was willing to get Hitler into power.
I might add there is a certain difference in how Japan and Germany view the war even in the present. While the German government and society generally recognizes war crimes, the Japanese government does not leading to controversies even now over her recognition of responsibility for comfort women (ie sex slaves) and forced labourers in Korea and other conquered areas. Rather than recognizing such guilt, Japan has imposed export restrictions on South Korea after courts in the latter country demanded Japanese corporations pay restitution to the few surviving labourers. This may be due to a variety of factors including a greater survival of the prewar Japanese elite and especially the Emperor himself who was never put on trial for war crimes.
