I really have my doubts that the asteroid impact was anything more than the final straw for the dinosaurs. Too many of the smaller more delicate critters did survive.
:’) It was the final straw — and it was also the first through final minus one straw. The surviving species were exactly the kinds which would (and did) survive the K-T impact event. The dinos were *not* in decline as a taxa prior to the event. There’s a massive resistance to the impact mass extinction model, and will continue to be, from the Darwin diehards; and there’s a massive resistance to it from the YECs.