Just checking that calculation at the beginning of the movie. The dinosaur killer was 6 miles across. Let's call it a sphere of radius of 5000m. Let's also assume a density of 2000 kg/m³, the density of Ceres. That means the mass of the impactor would be around 10^15 kg.

Assuming that it came from a very long way away starting with a gravitional potential energy of 0. It falls to 6000km radius (the surface of Earth), which means a GPE drop of 7e22 J.

Converting this to that all important scientific unit of "nuclear weapon", we're stumped as to which one. Little Boy or La Bomba? Assume La Bomba, with a yield of 50 megatonnes of TNT equivalent and since a megative of TNT equivalent is 4e15 J, then that means the impactor transferred energy on the order of 350,000 "nuclear weapons".