We have no way of precisely knowing the level of disturbance generated by the projected impact event worldwide. We project massive flooding in a belt downwind from the impact area from the precipitation of the steam generated. If Mesopotamia was hit then it is a certainty that North Africa and Southern Europe also received torrential rain. The trickier question is to determine the extent of tsunami activity. Tsunamis scour the coast as far inland as they go. They can be expected to rush up river valleys tearing up sediments and on reversing to take the bulk of these sediments with them, releasing most back offshore. Scouring does not leave a convenient sedimentary sequence. More likely it will leave non-conformities in the sedimentary record. Sunken deltaic deposits should be scoured worldwide in order to determine if this event occurred in fact. A massive non-conforming sunken flood layer of extreme thickness would be an excellent indicator.
The other problem we have is that the evidence for all tsunamis under 300 (estimate – sea level maxima at approx. -300 ft) feet in height is submerged. That still leaves two excellent places to look in any event. The northern shore of South America should have received a maximum tsunami inundation, as should the islands of the Indonesian Archipelago wherever insufficient coastal plain existed to absorb the inundation.
Massive debris fields should be discoverable somewhere. These are thick accumulations of knocked down trees that are slowly been converted to coal. There are plenty of isolated debris fields in the geological record representing a variety of local catastrophes over millions of years. We are looking for a global mapping of cases that can be carbon dated up to twelve thousand years ago.
The best piece of evidence to locate would be the hole left behind at the impact site. It might have a strong and deep circular magnetic signature. The second best evidence would be datable seashells and bones buried at high elevations with a broad confirming distribution pattern. Otherwise, the vast majority of supporting evidence will be underwater.
In fairness, there is a great deal of suggestive data out there. It has not been correlated or even identified as anomalous. Just as plate tectonics required widespread sampling and a joining of the dots, so does any other anomalous data. The difficultly has always been in motivating the observer to do his job when there is no acceptable working theory. How well have the erratics scattered about Europe been studied and mapped? The phenomena itself could hardly be better defined.
The existence of oceanic or even fluvial debris at high elevations in various locales is absolutely an indicator of past geologic disturbance, localized or otherwise. The evidence is ample and global in extent. Mapping such is a practical proposition. It is the lack of a non controversial model that has sapped the will of the professional observers. Recall that it was not until the eruption of Mount St. Helens that it became possible to fully reconstruct what had occurred at Vesuvius in 79 AD.