The asteroid weighs ~4.310^9 KG. If the impact speed were ~30 km/s [1], breaking it up in the atmosphere through friction would create about... E = MV^2/2 = 3

The asteroid weighs ~4.310^9 KG. If the impact speed were ~30 km/s [1], breaking it up in the atmosphere through friction would create about... E = MV^2/2 = 3.87 10^18 joules. For contrast, the energy released by the Tsar bomba was 2.45 * 10^17 joules. The Tunguska meteor impact was something on the order of ~1 * 10^17 joules. Even if much of the energy dissipates in the upper atmosphere, and does so over multiple seconds, I'd say that anyone within ~150 miles of the point of 'impact' will likely have a very, very, very bad day. [1] Which is a pretty bad case. The Chelyabinsk meteor was traveling at ~18 km/s - a 30 km/s impact would be close to a 'head-on' collision.