How large a body would it take to make a crater as wide as the Gulf of Mexico?

The Gulf of Mexico is the result of plate tectonics, or "continental drift," in which the plates comprising the Earth's crust change position over time. The Gulf did not even exist in the distant past, and its size and shape will slowly change as time progresses and tectonic plates move.To simplify matters, let's replace the Gulf with a perfectly circular sea having the same total area. The Gulf has an area of about 600,000 square miles (1,554,000 square kilometers), which means we can replace...