Is there a piece of upside down foreign crust in the USA? When I studied earth science, a lecturer mentioned that one of the anomalies that earth science hasn’t been able to explain is a piece of crust in the USA.

This piece of crust appeared to match very well with the crust of another continent, if turned upside down, and didn’t match the surrounding crust in the USA.

I can't find any information about this and I can't forget about it. Is there any basis for this claim?
Most probably, he was referring to the Brunswick Magnetic Anomaly: http://www.geosociety.org/news/pr/2014/14-22.htm

This is an area of lower-than-normal magnetism present in North America in the Southwestern United States. Note that altough it COULD be a piece of Africa, it could also be caused by something else.