It seems to me that fascism is a kind of industrialized reversion to feudalism, usually, it is true, from some form of capitalism. That is, the predominant political relations revert from, perhaps, market and property relations to personal and, one might say, tribal ones. The Fuehrerprizip is exactly what a militant feudal liege would demand from his vassals, returning to them, in theory, the same absolute loyalty that they offer to him along with submission. It has the glamor and simplicity of the wolf pack.
Therefore, fascism is a mode of the State, and any example of the State could be converted to it, including nominally socialist versions, given the right conditions (usually, some breakdown causing the established leadership to lose repute and authority during a serious crisis). That is because the germ of the State is the sociopathic relation of coercion. In fascism what was hidden becomes manifest.
I say "nominally socialist" because actual socialism, the actual ownership and control of the means of production by the people, can exist only where the State and its class system have been abolished. The only non-fascist state that can't be converted to fascism is the one that doesn't exist.