Well I agree that the FR didn't create nationalism but I think it generated a new
kind of nationalism, one that combined itself with other revolutionary ideas - as you say, if the HRE still exists, German nationalism would be focused on reforming and strengthening it, whereas the new nationalism the FR introduced in OTL was more about the people overturning the old order and founding new rationalist states.
Meanwhile, I invite you to join me in spectating as ImperialVienna and Nietszche re-enact the Seven Weeks' War

Okay, Ill try... starting at the comments I ignored at my last reply because I was about to go to bed.
Well - it did and would happen - but it would be dramatic and would shake the world, it wouldn't be casual; have you ever heard of the Diplomatic Revolution?
IMO, the Diplomatic Revolution is greatly overexaggerated. Prussia in alliance with Britain? Hell, that was the normal course of events for centuries. The real shocker of course was the Franco-Austrian alliance, but that more or less was caused by the Austrian-Prussian enemyship - and that in itself already was a revolution, seeing how Brandenburg-Prussia and Austria had fought side by side against France the entire late 17th and early 18th century. However, this "revolution" does get much less press, so I would say the (capitalised) Diplomatic Revolution is simply a bit, well, hyped.
...but as that has no bearing on the discussion, this merely as an aside
Well, Germany won't be a stomping ground for that generation's European conflict, which means a number of important things don't happen.
But seeing how pre-1815 Germany ALWAYS has been Europes military stomping ground for centuries - well, lets say if it arent the Revolutionary and Napoleonic Wars that are fought in Germany I do think some other europe wide cofnlicts, in the mold of the War of the Grand Alliance, War of the Spanish Succession, Seven Years War etc. will be fought in Germany. Of course, your conclusion is still right, because without the French revolution there will be no mass armies, and no outright dismantlement of defeated enemies - before the French Revolution that was... well, only most rarely done. So there would most likely indeed be no impetus for reforms. After all, as said, armies marching through Germanies? Thats the normal state of affairs.
Also, Germany is not destroyed again along the same lines of the 30 years war (which many contemporary writers drew parallels between to incite German popular sentiment, which wasn't helped by the French shooting civilian dissidents), it would be economically stronger and more populous.
Which however will unfortunately be more than evened out by the fact that the hundreds of custoim barriers in Germany will remain, and commerce laws will not be reformed. Early Napoleonic Germany, before Napoleon really robbed all manpower ressources, saw a bit of an economic boom after all.
Finally, the internal political divisions within Germany are not highlighted by having certain states (Bavaria to name one) fighting alongside France willingly.
Again, normal state of affairs as of the 18th century. Bavaria fought along France in the Spanish Succession already, and later in teh 18th century it was normal that different German states would take different sides. Such things wouldve been a shocker in the 17th century, but the 18th century? Not so much anymore.
All this likely also makes the popular revolutions of 1848 unlikely and more sedate reforms occur over a longer period. There is also unlikely to be a strong desire for Grossdeutschland, as much of the popular sentiment was based on patriotic feelings stirred up on the battlefield and stoked by student regiments that shed their blood for the idea of German unity.
Eh, Großdeutschland was the state of affairs in the HRE anyways... and as said, as the burgeoise grows, so will political awareness. It will not be as revolutionary most likely, but German politics simply will not be frozen in the 18th century. Of course, as said, wether this pressure for reforms (which Im sure will happeN) will actualyl suceed anything is highly doubtful. What I see is that eventually (basically, timewise, at the discretion of any timeline author, as the timing is so dependant on so many things) there will be a push for reforms of the HRE - but the HRE had seen dozens of such things, all basically fads that eventualyl faded again. And, sad as I think that is, I see no reason why this special attemnpt at reforms would be successful.
So I do see another war down the line, which, if it included the German states, something very likely, then it would have a similar effect to the Napoleonic wars.
I agree, as said. France very much was a dormant giant, and if not the Revolution, than something else will awake it. The question is the timing of course.
See, I think we need to find a middle ground here between Anglo authors' tendency to assume "Germany will remain small states forever with no inclination to get together, if the exact situation that led to unification in OTL is averted" and Susano's "every German peasant has had the burning heart's desire for a unified German nation state since 1648!"

This would make for a good ASBWI: People militias and French revolution style mass armies at the Grand Alliance shouting "1648 or Fight!"
One interesting effect of a no French revolution and no Napoleon timeline would be that the prince-bishoprics (much disliked as they are on AH.com) would still exist, although I must admit that I do not know what effect they would have on German unification.
Well, IMO, its no coincidence that the Mediation of IOTL targetted the ecclestial territories and the imperial free cities. Hell, already Sickingen's revolution of the Impeiral Knights in the 16th century had as aim the abolishment of the clergicla territory and their division among the knights (to ensure their survival as an estate). They werent targeted before because... well, such things simply were not (or only rarely) done in Germany. German states just did not do outright conquest of another. There was after all still the Imperial Court to settle dispuites (after oh, one or two decades of court suit...). That attitude of course waned during the 18th century, together with respect for the imperila institutions in general, but that was what protected the ecclestial trerritories. But youc an bet that should the situation become cut-throat in Germany, then the ecclestial territories and the free citie swill be targetted first, most probably even before the smaller secular territories. Especially since basically every middle power bordered at least some ecclestial territory, so it would be a winning situation for everybdoy!