The Mars astronauts thought they had had it rough, being chased all the way from Mars, then finding that there was no help from Earth with their re-entry - in fact downright interference. There are still elements that consider the returning astronauts a threat.
Part of Gran Canaria slid into the Atlantic Ocean. Vast areas of the eastern seaboard of the USA has been devastated by the resulting Tsunami, including most of NASA.
Now survival outranks the secret they are carrying; but which threat to them is greater - the unruly mid-west, or the enemies they fomented whilst they were on Mars?