Somebody is bound to ask this: When the US Government nuked Myrtle Beach, was there any damage?

The US Government nuked Quebec once in the 1950s.

Actually, the bomb in question was not "loaded" with a warhead, but they were forced to drop it--and then explode it in order to prevent it from falling into the wrong hands (Eskimo Nell? the Quebec Government?). The sound of the explosion was heard in five villages. Even without the warhead, the conventional explosives in a 1950s bomb was an impressive amount of Ka-boom!

Wikipedia:

November 10, 1950 - Rivière-du-Loup, Québec, Canada - Non-nuclear detonation of an atomic bomb
Returning one of several U.S. Mark 4 nuclear bombs secretly deployed in Canada, a USAF B-50 had engine trouble and jettisoned the weapon at 10,500 feet (3,200 m). The crew set the bomb to self-destruct at 2,500 ft (760 m) and dropped over the St. Lawrence River. The explosion shook area residents and scattered nearly 100 pounds (45 kg) of uranium (U-238) used in the weapon's tamper. The plutonium core ("pit") was not in the bomb at the time.[7]

This wasn't even the first nuke problem over Canada.

Wikipedia:

February 13, 1950 - British Columbia, Canada - 1950 British Columbia B-36 crash-non-nuclear detonation of a simulated atomic bomb
A USAF B-36 bomber, AF Ser. No. 44-92075, was flying a simulated combat mission from Eielson Air Force Base, near Fairbanks, Alaska, to Carswell Air Force Base in Fort Worth, Texas, carrying one weapon containing a dummy warhead. The warhead contained uranium instead of plutonium. After six hours of flight, the bomber experienced mechanical problems and was forced to shut down three of its six engines at an altitude of 12,000 feet (3,700 m). Fearing that severe weather and icing would jeopardize a safe emergency landing, the weapon was jettisoned over the Pacific Ocean from a height of 8,000 ft (2,400 m). The weapon's high explosives detonated upon impact. All of the sixteen crew members and one passenger were able to parachute from the plane and twelve were subsequently rescued from Princess Royal Island. The Pentagon's summary report does not mention if the weapon was later recovered.[5]

More:
http://en.wikipedia.org/wiki/List_of_military_nuclear_accidents

You can see why some people might protest the stationing of American nukes on their territory. Worse things have happened and in places far more heavily populated than Canada, but nobody likes their nation becoming a target of the world's massive arsenel of over-kill. Canada at least can sleep secure in the knowledge that Americans at least think it is worth protecting from the Enemy (even if it has to be destroyed to liberate it, to quote the Vietnam War era military-speak).

The percentage of Americans who would risk American hides for many other countries is small and the political costs of letting the Russians or Chinese have them, smaller.

All in all, Canada is fortunate that it has plenty of room and can absorb quite a thrashing without really noticing. As the old joke puts it: Canada plays an important role in American nuclear defence strategy. The Americans hope the Russian missiles will run out of fuel over it.

Although some of the more difficult to recover nukes are still lying around the ocean floor, corroding, they are probably nothing compared to the massive stockpiles of radioactive by-product (whole buildings, clothing, radioactive isotopes, ants that have crawled through the waste, etc.) that is just sitting around waiting for somebody to figure out what the Hell, if anything, they are going to do with it.

Nuclear power plants typically have large pools of waste like those at the Japanese tsunami-destroyed reactors at Fukashima. Some of them are on the coast and even more vulnerable to a tsunami or earthquake than the Japanese facilities.

A nuclear bomb isn't going to explode spontaneously (that we know) but these piles of untold tons of rubbish could be spread all over Southern California, the East Coast, etc., in the event of a big hurricane or tsunami. They are far from contained as it is. As hinted above, ants and termites and other critters have been found around the dumps (containment is too big a word) with enough radioactivity to alarm even pro-nuclear scientists.

There are a lot of economic costs not being fully accounted for, not to mention a lot of safety not being fully provided. The externalities of nuclear waste mount with the waste. We get the power right away, the next 450,000 years of humanity and life on Earth get the problems.

I don't think the kind of "discounting" that economists do should apply to human extinction risks. It's all or nothing, kids. If the human race goes extinct ten thousand years from now, it's just as serious and final as if it goes extinct today. You don't discount extinction. The value of future generations is not morally or even economically less than the value of the present generation. Future value discounting only works in microeconomic situation. In macro-economics it fails, and in the bigger moral picture, it fails catastrophically.

Call me a Burke Conservative, if you like. I think it is so.