For once I agree with Ensign, and would like to expand a bit what I think.
The reasons there have been no Italian world champions is specular to the fact there have been ten or so British world champions in the same time frame.
It is clear there is a direct relation between the backing coming up the ranks and then, crucially, the competitive rides available at the top level. This explains, also, why there have been so many great performers from Italy and Germany between the wars, and not from other countries: that is not independent from where the successful race car manufacturers of the era came from.
The rides available to the top British talent were cars capable to land world championships, in a time when almost all of them were British-based. The only Italian marque at that level – and still for long periods struggling to keep up to the new paradigm – was Ferrari who eventually declined altogether, for reasons not always linked to the quality available and by necessity (only two cars against all the rest of the grid), to rely on the local talent. In the end, the presence of the great F1 marque as national team, was a chimera that set back more than one promising career, that in a different context could have produced more results.
That also explains why, for example, despite the huge investment of Elf in the late Sixties and through the Seventies, a posse of talented drivers produced only a world champion, and not by chance an outstanding one at that, and crucially not on a French car: there were no world championship-material French cars on the grid available who could lead any of those drivers to the ultimate prize.
That also explains that when the sport’s centre of gravity started slightly to change, we saw finally the emergence of top talent from Germany: Schumacher from Mercedes, then through a multinational team (English-based, Italian financed and managed – Benetton/Briatore - thus a bit more culturally open than a fully English team) succeeded; Vettel, from the BMW junior team to the Austrian-financed and led (Marko) Red Bull.
That also explain, in my view, why a driver who in his second (and first full) F1 season could fight it out at the sharp end for then going through all that he went through after Monza 1978. Had he been British, I seriously doubt there would have been Hunt’s witch hunt, and he would have had a different treatment on the media – British first, of the country that provided the rides that mattered. That clearly changed Patrese’s career dynamics, in my view. When he went to Brabham - four years later - his mental ‘momentum’ had gone, besides all other issues related to the context.
Italy had a good renaissance of talent in the second half of the Seventies. IMHO, a couple of drivers among Patrese, Giacomelli, De Angelis and Alboreto, had they born with a British passport, could likely have landed a championship, not all-time greats perhaps (very few are) but still capable to do the job. Fisichella was quicker than Button, but it’s Button who had a championship ride in the end, after people (British) had long been querying whether he would ever finally made it.
Brazilian and Finns, to mention two nationalities that have been successful, didn’t have the distraction of a national race car industry, they had the hunger to achieve in an hostile environment that were not theirs from the start: that mental attitude produced some outstanding achievers. A mental attitude that often Italian drivers did not have, exactly because coming from Italy. The one that really got away was Zanardi.
Only want to mention, in the end, that I was huge fan of Alberto Colombo da Varedo, very dignified F2 privateer, and I respected Sigi Stohr, very talented at F3 and F2 level (ask Rory Byrne), but perhaps in the end too brainy for his own good to succeed where it mattered.
No, I didn't. Yes, I think this thread is going to produce a lot of different lists.
, Montermini, Brancatelli, Stohr). It seemed more of a surprise that any Italian anywhere near the sharp end of F2 or F3 never got a chance - the most egregious example being Maurizio Flammini. 
