how were these citizens different than e.g. the citizens of Italy, or Japan?
Japan was not different, according to the US at the time. The re-education soon renamed re-orientation (in both countries) program was active in Japan as well; the latter is just less well known.
And the US was actually more successful at reforming the Japanese education system than it was at doing that [themselves] in Germany.
Italy is a different story. It was treated differently in part because it overthrew Mussolini itself, albeit belatedly. So the AMGOT lasted much less in Italy (end of the war.) The job of re-education was left much more the Italians themselves in that case.
If you need a more comparative (and much less optimistic) view
Although Germany was the crucible of Allied re-educative ambitions, the American-led military government in Tokyo also strove to de-Shinto-ize, de-militarize and de-cartelize Japan, while simultaneously effecting a thorough reorganization of Japan’s educational system. ‘Freedom of speech, of religion, and of thought, as well as respect for the fundamental human rights shall be established,’ the Potsdam declaration averred.
Historians of postwar Germany and Japan have thoroughly examined both of these ventures. Noting a terminological shift in favour of ‘reorientation’ towards the end of the 1940s, the German term ‘Umerziehung’ always freighted with Nazi connotations, scholars have located the western allies’ transformative ambitions within the larger matrix of postwar geopolitics. As tensions with the USSR hardened into a state of permanent cold war by 1948, Washington’s overarching goal increasingly appeared less punitive than strategic: an attempt to anchor the liberal-capitalist system in Western Europe and East Asia through reoriented former foes turned allies.
And the British tried to re-educate even more peoples, in nastier fashion, at around the same time:
In parallel, scholars have dissected the various projects termed re-educative or rehabilitative by British administrators of colonies roiled by anti-colonial violence in the 1940s and 1950s, as National Servicemen swept Malayan ‘insurgents’ and Mau Mau ‘terrorists’ (among others) into camps that purported to remodel their inhabitants as pacific and pliable subjects. With approximately one third of the adult male Kikuyu population incarcerated, Britain’s ‘re-educational’ ventures reached their apogee in Kenya during the colony’s prolonged Emergency (1952 to 1960). These and other colonial carceral exercises have been subjected to substantial historical scrutiny.
To say nothing of the Soviets' re-education efforts, but you only seem interested in Western allies.
Anyhow,
Over time, scholars and policymakers have increasingly come to locate the re-education of Germany and Japan along a continuum of US-led modernization schemes, stretching from the fin-de-siècle Philippines to twenty-first century Iraq and Afghanistan – rolling manifestations of the ‘redeemer nation’ at work. [...]
By the early 1960s, re-education and rehabilitation seemed to vanish as descriptors that British and American policymakers and military commanders applied to their own actions. Along with a parallel language of ‘brainwashing’ and ‘thought control’ – terms that first emerged from the fledgling People’s Republic of China (PRC) and then Chinese-run POW camps during the Korean War – re-education (in Western European and North American parlance) increasingly became something ‘they’ did on the far side of the so-called Iron and Bamboo curtains.
TLDR for the latter part of that paper: it's not that the US (and Westerners more broadly) didn't try to re-educate Afghans or Iraqis, they just didn't call it that anymore. (Even the ‘O-word’--occupation--became somewhat taboo in this century.)
