We're told that regime change and occupation fuel extremism and radicalization anywhere regardless of ethnicity and ideology, then perhaps remnant German Nazis and Japanese jingoists could teach the Americans a lesson which they later learnt in Iraq and Afghanistan.
Afghanistan was extremist well before American intervention (stoning individuals in soccer stadiums, destroying millennia old artifacts, adhering to an ideology that rejects humanism, technology, and free thought). The Taliban are a minority succored by their neighbors who harbor them as a buffer against neighbors as well as a subtle extremist bent.
Iraq is largely due to a privileged minority losing their rights, disenfranchised and disillusioned, grabbing for whatever opportunity they have for a return to control.
The horrors of Okinawa, Hiroshima, Nagasaki as well as the firebombings of Dresden, etc are not known to these people, nor the horrors of a vengeful occupation.
They see Americans as an invading force, understandable as we are more different than those they have suffered under. But the extremism seen is by a minority determined to win a PR battle rather than a cultural one.
What is seen as local extremism is nothing more than excellent propaganda by outside powers meant to sap the resolve of both natives and foreign forces.