Why did cougars survive in North America but jaguars did not?

Jaguars once roamed as far north as Washington, Oregon and Pennsylvania

The fossil record suggest jaguars, along with dire wolves, were the most common large carnivores (excluding omnivorous bears) in southeastern North America during the Pleistocene. Yet, cougars found their niche here too. During the Pleistocene both species were somewhat larger than the present day versions of these species. Rancho La Brean specimens of cougars show that on average they were 5% larger than those of today, while Pleistocene jaguars approached modern day tigers in size. I think this is due to the larger size and quality of prey available, particularly horses and the larger sized species of peccaries, and it’s clear these two big cats not only had a better diet, but further impetus to evolve to a greater size, so they could successfully exploit this larger prey. One study reported that modern jaguars living in areas where cattle were introduced tend to approach the size of the larger Pleistocene jaguars, and it’s believed that jaguar populations increased following the introduction of European livestock to South America.

When did jaguars disappear from eastern North America? 

Giant cats of the Pleistocene