Completely feasible, we have over a hundred nuclear reactors operating at sea safely for a few decades. You can call Rolls Royce right now and sign a contract and they can build everything you need by modifying and assembling parts and designs they have in stock and have it in production in 5 years including a couple tankers. You could call General Dynamics and they can do the same thing. It's not a problem of technology, it's a matter of will and financing.
The reactors are not so much the question in my mind. As you point out, there are many U.S. naval ships powered by nuclear reactors. Although the economic feasibility is a bit of a question in my own mind, at least. That something can be done by the military doesn't necessarily mean it will scale well for domestic use. Not that I am saying it won't wiork, it's just that I have no idea. My real question is the fuel cell technology. The last presentation I saw on hydrogen fuel cells indicated it wasn't yet ready for prime time, but I do not claim to be an expert on that technology, either. Hydrogen combustion would obviously be very "green," as the by product of the combustion is simply H20. Some day we will make it work. Or at least we will make something work that is even better. . . .