A Tunguska-scale impact over a major city today would produce millions of casualties and tens of millions of injuries. The 1908 event flattened 800 square miles of Siberian forest with an airburst estimated at 10 to 15 megatons. No one died because the region was uninhabited. That same energy release over New York, London, or Tokyo would be catastrophic on a scale difficult to comprehend. The blast wave alone would level infrastructure across an area larger than most metropolitan cores.
This isn't speculation. It's math. The question isn't whether such events can happen. The question is when, and whether we're prepared to detect and respond. The Tunguska object was likely only 50 to 60 meters across. Objects of that size are difficult to track and arrive with little to no warning. Understanding the risk means understanding the frequency, the energy involved, and the consequences of impact in populated regions.