He could float one over, and cause cataclysmic problems.
In fact, he could float one over to Mexico, which is one of the most corrupt countries on the planet where there government officials can be bribed with cheap prostitutes and a bit of cash..
It would be easy.
That tractor trailer parked at Walmart in Austin Texas, instead of being smuggled across filled with typical 75 Mexicans and 2,000 pounds so dope, could possibly contain something much more dangerous.
Tsuamis nowhere, even from a multi-megaton thermonuclear device. The distance from a blast with waves of any significance is measured in a few miles, at best.
A tsunami-causing earthquake's energy makes the energy of even the largest nuclear weapons look like a joke.