Cardi B created a firestorm with the whirlwind news of her divorce and pregnancy -- but a new song that's out aimed at her soon-to-be-ex-husband Offset has people buzzing too ... even though it's really much ado about nothin'.

Here's the deal ... right on the heels of Cardi's divorce news, a song surfaced on YouTube that was being attributed to Cardi -- and it was being advertised as a diss song at Offset ... which was titled 'Tia Kemp (It's Over)' ... and it sure sounds like Cardi rapping on the beat.

There's a pic of Rick Ross' ex Tia Kemp on the album art for this -- which had people confused as to whether this was actually Cardi crapping on her estranged hubby. Well, as it turns out ... we know that's not the case.

Sources with direct knowledge tell TMZ ... the track is 100% AI and NOT from Cardi's upcoming album. In other words ... she has nothing to do with the making of this.

The tacky track features lyrics about having to move on after spending lonely nights alone -- but every one of AI-Cardi's words sound copied and pasted onto the track, not to mention the flimsy Yankee Doodle drumbeat doesn't sound like anything she'd ever rap over.

Sources close to the couple relayed to us the split is completely amicable after they attempted to make it work all year, so a diss track doesn't even make sense in that regard.