Apparently the U.S. was a favorite target for hits delivered from outer space.
Every year more and more sites from this period are being discovered indicating a very high level of technology. I think many of the mega structures in Egypt, and South America are far older than people think, and especially in south america there are many locations that seem to have two levels of technology. One is the 100 ton stones cut with laser accuracy, and then a level on top of it constructed with far less technology much later. Every year more and more sites world wide are discovered that all seem to date around 12,000 years ago. Archaeologists do not like to talk about them because it challenges the civilization myths and some imply that other peoples inhabited the americas before the indians came and to speak of which is career ending to even whisper.