What do you mean? People in the US routinely use "quarter after" and "quarter to" when telling time.

No, its absolutely widespread that they do.

You can confirm this by searching "quarter past" at any significant US website, e.g., the NY Times:

<https://duckduckgo.com/?q=site%3Anytimes.com+%22quarter+past>

"Quarter of" or "quarter to" are less frequent, but can be found and heard.

I've only ever lived in NE USA, but I have traveled, and I definitely don't think it's regional.

Generational though, sure.

Oh yes, I grew saying "quarter past four." Probably don't anymore, but it was definitely in the vernacular in the US in years past.