Is there any reputable source for this claim? Apologies if I missed it but didn't see one linked in the article. I ask because it's not what I'd read or understood yesterday.

No. Only unnamed sources. I would say it is more likely a balloon than not though. Both stories are perfectly believable, a mylar balloon is def going to show up on radar, and the cartel does use drones. I think the balloon story is more believable though because the cartels would gain almost nothing from this, and if it was a drone I would expect photos of the debris by now.

All of the "reputable" sources appear to be relying on "highly placed" anonymous sources, and many of the articles conflict with each other.

Could have been little green men! But what exactly happened is probably (or should be) classified.

What you read yesterday was most likely a deliberate lie to cover up dysfunctional federal government agencies:

https://www.cbsnews.com/news/airspace-closure-followed-spat-...

Yes: https://www.cbsnews.com/news/airspace-closure-followed-spat-...

FAA Administrator Bryan Bedford on Tuesday night decided to close the airspace — without alerting White House, Pentagon or Homeland Security officials, sources said.

...

Customs and Border Protection used the laser weapon earlier this week after training from the U.S. military, according to multiple sources familiar with its deployment. Officials had recently given the FAA a 10-day window in which the technology would be used.

The anti-drone technology was launched near the southern border to shoot down what appeared to be foreign drones. The flying material turned out to be a party balloon, sources said. One balloon was shot down, several sources said.

The Mexican cartels have been running drones on the border lately, the sources said, but it was unclear how many were hit by the military's anti-UAS (unmanned aircraft systems) technology this week. One official said at least one cartel drone was successfully disabled.