I'm wondering if dinosaurs had high oxygen requirements, and the event reduced the Earth's O2 level for a while and they suffocated. It's one thing which would explain why all dinos everywhere, both land and sea dwellers, on all continents, died.
Avian dinosaurs would have needed extra lung capacity for flight, which would have allowed them to survive a lower oxygen level and feast on the carcasses of dead dinosaurs.
The dust from the event is believed to have denied sufficient light to support photosynthesis and thus most plant life died. With that, herbivorous dinos died off, and then the carnivorous ones who depended on them for food.
Whatever you are smoking must be the good stuff.
Pretty much every land animal that survived the Chicxulub impact was a burrow dweller/nester.
Nothing much larger than a house cat made it through.
Given that, I’d guess the surviving early birds were like modern puffins, or burrowing owls, to name only two of the numerous modern examples.
AND, burrow dwellers live, nest, and sleep in confined spaces, which due to respiration and relatively poor ventilation, have lower oxygen and higher carbon dioxide levels.
This is like training wheels for devastated earth’s thinned and scorched atmosphere!