The interesting thing about Astérix is that not only it was the result of the popularized image of Gauls since the mid-to-late XIXth century, but that it actively defused it trough sheer comedy, dressing mid-century French society with a superficial clothing made out of images d'Epinal (more or less naive and popularized printed pictures).

At no point Astérix was understood as depicting any sort of historical reality, safe for dressing the narrative into a familiar yet exotic landscape (contrary to Alix, an earlier comics that focused on historicity and peplum qualities), Goscinny and Uderzo precising regularily that didn't even attempted to do so (famously, Uderzo received praise for its description of a Roman harbour, but saying it was completely accidental). What they popularized were clichés and tropes on Antiquity, mostly for comedy values, and often (excepted maybe in the first stories) mixed up with modern references.

The brave and fearsome warriors are turned in a bunch of idiots whom reactions were modeled on this annoying neighbour or your brother-in-law; the most brave and strong of them is a foolish manchild, the most intelligent is an irascible dwarf and both are far from the idealized depiction of a Gaulish warrior; Getafix isn't a practicer of human sacrifice whom authority could raise rebellion but a gentle old man; rather than moving souls the bard is universally loathed by the village, etc. The village is obviously a redux of the French society of the time, Romans being less depicted as foreigners or invaders (except for the legions) but as a "modern" people, already at home in Gaul and not even using a different language than Gauls (contrary to, say, Egyptians). Corsica, Britain, Spain are defined by contemporary idiosyncracies (such as Beatles-looking bard in Britain; Germanic tourism in Hispania, etc.) with maybe some remembrances of Latin erudition there or there.

These references echoed among readers (possibly more to adults readers than children, Astérix being the first comic in France to be openly read by adults) because they were part of the classical references in French culture widespread trough mandatory education, popularization of classical culture (the famous "pages roses du dictionnaire" an infold list of Latin expressions in dictionaries), cinema (which is made obvious with Astérix et Cléopâtre), etc. Interestingly, in these references, Gauls had a ambivalent place : Lavisse's Histoire de France, a texbook for elementary classes, doesn't talk much about them in the chapter about Gauls and Romans, only to say to child they were savages-like, miserable, and telling child "you wouldn't want to be ignorant like [Gaul children]". They were brave and fierce, but fortunately Romans conquered them and taught Gauls what civilization was (if you see a parallel with French colonialism, it's because it was precisely that too : a speech of Napoleon III promises to Algeria conquered by France a similar fate than ancient Gaul

This ambivalent reputation of Gauls in French academia began in the XVIth century, with repurposed classical studies and display : as the idea of a French nation began to emerge, it was made clear that the "first people" inhabiting its territory were Gauls, not Romans or Franks. A certain enshrinement of his idea of Gaul, rather than Gauls themselves continued up to the XIXth century (for instance, with Henri Grégoire calling out french nobility claiming to descend from Franks by saying that they could go back to their primeval forests if so, France "being happy being inhabited by the descendants of Gauls and Romans only" then, sort of historiographical "we, the people"). But in spite of the interest of several academicians that shaped the image of Gaul as barbarous but romantic and exotic ancestors who already had a potential for greatness fuliflled by the Roman conquest creating a "Gallo-Roman" culture, the best of both worlds (Gallo-Roman culture being a concept under heavy criticism currently, mostly because the Gaulish influence on Roman Gaul is particularly limited).

The archeological discoveries, and the literary build-up (notably the Irish literature), also reinforced the idea of Gauls as the "prime" people of France, which with the rise of modern nationalism (and the impossibility to claim Romans as "unique" ancestor, or Franks as far too associated with the Ancien Régime), which either pushed to a certain folklorism (with a regional backlash with the promotion of local peoples as distinct and regional ancestors : Bretons, Ligures, Norses, Basques, etc.) and at worst a lukewarm racialism (people outside Gallo-Roman population being necessarily foreign, regardless of how long they were settled or not : Jews, Italians, Germans, etc.) It's hard to consider the idea of a state-promoted Gaulish identity, and while mandatory education was certainly a component as was the Académie Française into its institutionalisation, it was also a matter of popular culture and of various historiographies where both liberals and nationalists could find something.

This was the cultural background on Gauls, although tempered by serious studies as Camille Jullian's and Albert Grenier's in the first half of the XXth century, Astérix was first published in 1959, more shaped than shaping anything, turning all of this into comedy stock and, doing so trough blurring the line between ancient Gauls and contemporary French up to the absurd, might have done their lot defusing them as the archeology and history of ancient Gaul went trough sort of a scientific renaissance eventually (we might illustrate trough the discovery of Vix Grave in 1953), never "updating" the comics whom this absurdity was one of the main comedic devices (although Pilote, the magazine Astérix was originally published in, took great care having educational pages about ancient Gauls, such as "Un oppidum gaulois" in the n°68).

It could be summarized that Astérix emerges in a France that is no longer a colonial power, which is undergoing a quick and culturally difficult modernization : were a comic as Alix promotes seriously the old idea of Barbarity vs. Civilization and the necessity of change for the best (although backtracking a lot in the 70's), Astérix promotes the idea of a society not necessarily benefiting from changes (Le Domaine des Dieux) but willy nilly part of it (Astérix aux Jeux Olympiques).

Eventually, "misconceptions" would imply that blatant anachronisms, unattested depictions, or the use of imagerie d'Epinal (to not even mention that the adventures take place in a perpetually happening, and necessarily fantastic, -50 BC),would have been done entirely by mistake; so rather than pointing out that, no, Antar/Michelin (Astérix et les Helvètes) didn't existed in ancient Gaul, I'll focus on depictions that don't carry a satirical or already obsolete point of view when it was published, and that might still be part of the popular perception of Gauls, which are essentially tied on the everyday life of Gauls.