This isn't the fault of the DHS - they're just trying to save themselves some trouble by trying to control the airspace of foreign nations rather than their own land and sea borders with those nations. The real blame falls on the governments of Canada, Mexico, and Caribbean countries for giving in to Continentalist pressure and allowing a foreign nation to dictate how they should operate. As a Canadian, I'd give my prime minister shit for this, but unfortunately he's already shown enough contempt for the interests of the Canadian people to make it a futile exercise.
What I want to know is what will happen if a flight from London to Havana does not supply DHS with the required information, but flies anyways? Will the US air force scramble fighter jets to shoot it down over international waters? Or will Cuban jets be scrambled to repel the flight out of Cuban airspace? Or will British jets circle over London to prevent take-off? Or does the flight land on schedule, and then the offending airline just quietly fires the pilot and flight crew in order to prevent US airports from boycotting the airline in retaliation? If they do fire the offenders, what would be the response of the pilot's union - would they go on strike over it? I really want to see this happen.
Or else, I'd like to see all the affected airlines make an agreement to simply refuse to fly to any US destination until the demands from the DHS are withdrawn. The move would probably put the airlines out of business, but it would be awesome nonetheless.