I'm not sure what Napoleon himself thought of Italian nationalism (though the contrast of the Napoleonic period with the subsequent reaction/Restoration was important in its development), but he definitely claimed to support Polish nationalism (though he was also using the Poles) and a lot of Poles fought for him. Both of these issues could be seen during the Restoration as as much an anti-Austria/Russia/Holy Alliance issue as anything. However, I am extrapolating from Napoleon himself, and the later actions of Napoleon III, because I don't know anything about contemporary Bonapartism

Again, the Emperors supported these things insofar as they were also beneficial to themselves.
Spanish nationalism per se wouldn't be an issue in the Restoration period, since they were independent already, but I doubt any Bonapartist would have anything good to say about the way Spain fought for independence from the Empire. And the Restoration-era French intervention in Spain happened before Marius's political awareness. So I have no clue, without actually doing research, what would be the issue there.