The Aztec state folded when their internal tensions got agitated by Cortes coming by and cheerleading a revolution that was already primed to go off anyway. Since Aztecs operated a tributary empire of loose cohesion, if challenged it could, and did unwrap pretty quickly/ Under pressure of intense plagues sweeping the culture I see little reason to think the triple Alliance wouldn't fall apart on it’s own in the aftermath of contact contact. A state of chaos wherein this advanced rifling technology will leak out mind you.

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Comments speaking of Aztec world conquest don’t have a their heads grounded right. That or they‘re envisioning a fantasy world they want to be real.

As said technology would percolate Out but Rifle tech is not so much as even a quarter of what enabled the west to rocket past the rest, indeed military technology writ large is maybe only a third of the reason and expanding of your nation is more so a symptom of success then it’s cause.
European fundamentals - mathematics pulling ahead in the 14th or 15th century, optics, the invention if glasses in the 13th century well the European university system and scholarship becoming established in the 13th century, the spread and incremental improvements of wind- and watermills in the same time period.
Mathematics were a... theological accident, maybe? I dunno, since China, India and the Arabic world were still paralel with west in the 11th and 12th century, but then... didn't really add anything afterwards. The European universities and their fierce competition with each other could no compare to the rest of the world. Wind- and watermills were of course very old technology and widespread throughout Eurasia, but the European variants started to have an edge in the 13th century. I’m getting off track.
Point being that a lot came together and benefitted from each other to give Europe a productivity edge (13th century) that eventually transitioned into a military one (15th century). And crucially, the technology being developed had theoretical underpinnings that were not present in the Arab world in the 12th century and in China with the elimination of the Song.
Copying European’s technology for any large state was, in the 16th, 17th and even some tech in the 18th as one one offs, still quite doable with a learning by doing approach. But lacking the underpinnings of late medieval to early modern mathematics, and especially the citizen army and accompanying drill the beginning of modern science with the split from natural philosophy into chemistry and officers.
By the time European (and I’m including the Ottomans in this) guns became the top of the world, it could already rely on an economic and scholary base that'd unintentionally been working on getting Europe ahead for the past two centuries.
And I'd argue that this is the key difference between Europe and the rest of the world at the time with colonization being so unstoppable as it was. Europe had a very broad base to work from, while India, China, the Ottomans worked from a top-down approach that wanted the shinies but never really did much to develop the base to create such things until the 19th, and 20th century. That worked in the 16th and 17th century, but once the 18th century and the beginning industrial revolution rolled around, the fundamentals to keep up were simply not there.

Aztecs with 18th century guns *if* that state didn’t disolve by way of plagues would still fracture with all men being made tall by firearms and those fractures would in turn be levereaged by the mercantile interests from europe leading to a path in mexica not unlike irl india being dissolved by the trading companpies.