There is no genuine question about whether jihad today is defensive or offensive. I am not aware of any of the jihadi groups declaring that their aim is to conquer the West and impose Shari’ah in the US or France or anywhere else, except within our own lands.
Whether we adopt the conventional (and in my view, obsolete) methodology of armed struggle against the security forces in our countries, or against the military forces of the West that have invaded our lands; or if we adopt terrorist tactics against either Western or domestic targets (a counter-productive tactic in my opinion); or whether we engage in systematic economic disruption of multinationals and the interests of foreign investors; all of this is defensive in nature.
Defense of the Muslim lands, liberating them from foreign domination, reclaiming independent sovereignty to establish Shari’ah in our countries, is obligatory and does not require the presence of an imaam or the issuing of a governmental order. There is no difference of opinion in this regard, as far as I know.