And I am surprised NOVA did not mention them.

First, the planet was a lot warmer then, there were no ice caps, sea level was a lot higher, the center of North America was flooded from north to south with a shallow seaway.

https://en.wikipedia.org/wiki/Cretaceous_Thermal_Maximum

Second, recent paleomagnetic studies suggest that Alaska was much further south, anywhere between 32 and 55 degrees north.

https://pubs.geoscienceworld.org/gsa/geology/article-abstract/29/10/947/191900/Late-Cretaceous-paleogeography-of-Wrangellia

It rather difficult to tease some of these things out of the paleomagnetic data, the difference between magnetic poles and the tilt of the earth itself. Both are dynamic over geologic time.

https://www.sciencealert.com/there-s-evidence-that-earth-tipped-on-its-side-84-million-years-ago

Did the show include a discussion of paleobotany in that area?