So let's actually go with both possibilities. How does the Italian campaign shape up without Napoleon? Could France have sustained the wars for longer without him?
If the Napoleonic wars never happen, what precisely would happen with an earlier Congress of Europe? The political butterflies of *that* would be pretty massive.
On Italy: France could most likely sustained the wars. There were generals besides Napoleon after all, and France still has plenty of manpower and revolutionary manpower to spare. If Desaix survives Marengo, he could lead a renewed offensive. Massena and Kellerman could also lead a victory here. Neither of those men have the political ambition Napoleon had though, so they wouldn't do much beyond that.
If there was such a ceasefire, Europe would set back to the pre-Revolutionary status quo antebellum. Austria would get Venice and Lombardia still, but Prussia would get none of the territory it gained from the congress, and still have Warsaw and the rest of inner Poland. This also prevents Russia from having excuses to go to war with Sweden over Finland and the Ottomans over Besserabia, at least for a while. France
might be able to retain Wallonia at best, but if the Royalists take control again they'd probably give that and the rest of Belgium to the Austrians.
Europe proceeds to develop and liberalize much slower than in OTL most likely. Without Napoleon's
massive changes to the political landscape, Republicanism and Nationalism don't have as much of a sway in contemporary life for the European citizenry, though they would still have some hold. Spain keeps her American colonies for a little while longer, 'til some opportunity presents itself for those lands to rebel. America probably won't get to the Pacific, with the eyes of Europe not distracted any longer. The U.S might take Louisiana still, by force or by trade, but I wouldn't expect them to get beyond that with the Brits watching them more. If there is a War of 1812 analogue in this timeline, America's ass would be kicked even worse than in OTL.
And that's just a few of the changes that would occur. As you said, the butterflies would be incredibly great.