This asteroid is about as big as an aircraft carrier. If it hit, it might result in a 4,000-megaton blast, a 7.0 earthquake, and (if it struck water) 70-foot-high tsunamis in the very immediate vicinity. An impact of that kind is estimated to be about a 100,000-year event. In contrast, the 65-million-year-old K-T boundary "dinosaur killer" probably was 5 or 10 miles wide, and that is considered about a 100-million-year event.
One of my favorite scifi stories is "Lucifer's Hammer," a TEOTWAWKI fantasy about a comet strike.
Asteroid guru Jay Melosh of Perdue University adds that "Apophis, a similar-sized asteroid about one-third of a mile in diameter, is the biggest threat in our near future. It has a tiny chance of striking the Earth in 2036." Yeah, that's what they said in Lucifer's Hammer. It's always a tiny chance until it happens! Nevertheless, although an object of that size might wipe out a big city, it probably wouldn't lead to any extinctions.