The map of earth's surface looked a lot different 250 million years ago assuming the continental drift model. All the continents were joined together into one, apparently. Did something happen to cause them to start to break up and begin drifting to their present locations all over half the planet? The other half being the Pacific Ocean.
Earth had a mobile crust before the PT boundary. As best we can tell, plate-like tectonism began in the Archean (early Precambrian), over 3 by ago. The continents were quite small then, and grew by accretion of terranes over the next 2.5 billion years. Pangea was only the last time that all the continental masses happened to be in close proximity. When it split, it was because of massive rifting in many locations. An impact-induced cause is neither necessary nor adequate to explain it.
I've often speculated such was the case. It might be fruitful for experts to investigate why Pangaea started to break up after what appears to be a long period of equilibrium. I wonder a lot, as well, about what kinds of events were involved in bringing deep plutonic rocks like Kimberlites to the surface in Africa, Siberia, Canada, Australia and other regions where diamond "pipes" are found. Could they have been the result of powerful impact events?
The theory of Pangea is interesting but I would like to hear more of how a single continent originally formed or split and reformed to a single continent again. Some of these theories move continents around to fit the "disaster d'jour".