There is no reason to think that the Earth had not taken as many hits proportionally as what we can see on the Moon. Yes our atmosphere is going to break up the asteroids more but it should be about the same.
It is interesting that more and more evidence is piling up to support the hypothesis in Firestone et al.’s book. The article talks of the ice age ending at the time of the Younger Dryas which was then made worse. My understanding is the the ice age was ending around 15 to 18,000 years ago, and that this event/series of events triggered the Younger Dryas. Firestone’s book documents very widespread effects from Canada to our Southwest and even northwestern Europe. My vote would be for more than one impactor. After all, remember how many boloids struck Jupiter a few years ago.
The Carolina Bays are one such phenomenon possibly caused. My guess is that huge blocs of ice were thrown out, skidded to a stop and melted. Lake Michigan appears to have been formed by 2 or 3 impactors whose traces are found underwater. The Clovis culture was decimated as were large numbers of the great mammals.
The Tungusku event was small by comparison. A similar event occurred in the Brazilian jungle several decades later but was somewhat smaller in size. We are only beginning to appreciate the impact of boloid events on our earth and our history. Sunken Civ has brought to our attention the discover of a 2 mile crater in the drained Iraq Marshes whih fell about 4,000 years ago. Was this the cause of the First Intermediate Period in Egypt about that time? Ipuwer records a time of terrible social upheaval and distress in a papyrus. There are also fairly large meteor craters found in Argentina around the same period or perhaps a little earlier. So much to learn, so little time!! But first we have to use our open minds.