The entire Atlantic Coast of both Europe, and North America, not to mention the Caribbean are at the very least devastated. A whole lot more than a million people are dead. Where the Tsunami went back out, it scoured the earth with the remains of what it destroyed on the way in.
But it just doesn’t make sense to guess, since there is no consistent scale for this event. A five hundred foot Tsunami is going to destroy everything for miles inland, but mostly along contour lines. It probably won’t have it’s full force at Washington. There is a lot of land, although not too many hills between DC, and the Atlantic. But the Southern Chesapeake is going to let the force come way up north much faster.
But what about the rebound Tsunami? We just blasted a big hole in the middle of the Atlantic Ocean. We moved a huge amount of water out, some up into the air and some just laterally away from the center. But when the energy is done doing that, the hole will fill in. And that is very big slosh. No, not a five hundred footer, but a bigger tsunami than you see most centuries.
There is a brand new rupture in the middle of the ocean floor in the Atlantic. This has huge consequences over the next thirty thousand years, or so. The circulation of water in the Atlantic is the largest driving force in the weather over most of Europe and Western Asia. What ever actually happens is going to be different than what happens now, on a global scale.
As usual, the perspective boys blew it on the picture of the impact. That sucker was gigantic. It was hundreds of miles in diameter, and the fireball was thousands of miles wide. That kind of energy is orders of magnitude greater than the described results. It makes no sense to try to model the results. Water vapor would stay at saturation levels for months, perhaps years. Water plumes heated by magma on the ocean floor could produce “Hypercanes” for centuries. (Consider that sunshine causes dozens of Hurricanes by raising the temperature of the ocean’s surface by single digit amounts.)
We would survive, as a species. But it might be a much different world, with Ice over Europe, and swamps and jungles over the Gobi, or Sahara. Political adjustments could well be significant.