I was wondering if this song, Feliz Navidad, is just an old holiday classic in the USA, or maybe it’s as common in Mexico, for one as, say, “Jingle Bells” is in the USA?
BTW, I never studied Spanish. Please feel free to correct my spelling of this Spanish phrase (claus? ho-ho-ho!). 
I’m confused about the question. Are you asking if Feliz Navidad is commonly sung in the US, or are you asking if it’s sung as common as Jingle Bells is in the US but in Mexico? Or are you asking both? 
Well, I am 1) not a native Spanish speaker, 2) not Mexican, and 3) Have not been deep into the heart of Mexico.
But…
I teach Mexican immigrant children, and the vast majority of them know this song. Take from that what you will.
[sub]ah, anecdotal evidence. but it’s somethin’[/sub]
My understanding is he’s asking whether it’s essentially just popular in the U.S., or is it a traditional Hispanic song, the way Jingle Bells is a traditional American song.
“Feliz Navidad” was written by Jose Feliciano, a native of Puerto Rico, in 1973. I refuse to accept anything created in my lifetime as “traditional” or an “old classic”!!!
“Feliz navidad, feliz navidad
Prospero año y felicidad”
Rinse and repeat.
It is a modern song. But there are many other traditional Christmas carols.