Yes, you are right, I think directly after 9/11 it would have been possible to convince a majority of the European public.The media transported quite a part of the shock the Americans felt then and most people judge with their gut.
But therefore I doubt that this opinion could have been conserved until now, unless tremendous progress in the nation building could have given an ex post 'humanitarian justification' for it and
"3) commit serious resources to Afghanistan (not point talking if it's anything under 300,000 US combat troops)" will be interpreted as escalating the war.

Der Amerikaner ist die Orchidee unter den Menschen
Volker Pispers