Always been fascinated by the "Shock Dynamics" Theory versus the slow Continental Drift Theory.
That, and where the hell do all of the odd socks go....
Like most things, why is this an either/or proposition?
It could be both. Great impact events causing more intense global action, and then drift when things are more quiet. This 300 mi+ crater is certainly huge. Regarding the shape of the Gulf of Mexico, are you referring to the coast line of US into Mexico, or the crater hitting part of Yucatan and extending into the GUlf? The Yucatan crater which occured around 65 million years ago apparently triggered the death of the dinosaurs. It is 150 to 180 miles wide, but does NOT touch our southern shoreline.
If the subject crater is precambrian, that is certainly older than the Yucatan crater that ended the dinosaurs. I took have wondered about the huge bay in Canada. Another really large one in, I think Ontario, produced a highly mineral rich and human exploited area called the Sudbury. Drove through it once, really a visual mess. I think several even earlier ones occurred more than 1 and 2 billion years ago as well.
Another one that has raised questions for me is the Great Permian Extinction event. Much worse than the dinosaur Extinction event, perhaps around 250 million or more years ago. Has been blamed on huge effusion of lava in Siberia, but did that happen as a volcanic event, or did a very large meteor strike, and get swallowed up by all the magma that flowed out?