Yaarel
🇮🇱 🇺🇦 He-Mage
That combination of both California and Ohio using y'all, suggests it is becoming American neutral.Yes, y'all is colloquial and not formal, so for formal usage you are correct.
In terms of real world usage, between Calkfornia and Ohio I have e seen y'all become more and more frequently used by people irregardless of regional accent over my lifetime, at an accelerating rate, too. As some with lhistorical literary and linguistic training, it has been a fascinating "on the ground" example of language shift in the past few decades.