MCM, I believe the OP was trying to get his head
around the tax implications and whether dual citizenship might somehow be worked to an advantage. I think you are mixing cruising in the US with permanent importation of a vessel to the US. I agree with the second paragraph but these rules address/reflect reporting requirements (ie: what is required of foreign and domestic vessels to cruise
in US waters) not permanent importation of a foreign vessel.
With regard to your first paragraph, I also agree as it applies to cruising but not importation. Were this true then every US citizen could simply buy a boat from any foreign country and import
it into the US permanently without having to pay any duty or tax whatsoever. Why would anyone then ever buy a boat in the US?
In Hpeer's case, it matters not as to which of his two hats he wears, US or Canadian. If he maintains the Canadian registration
he will be subject to the cruising rules / reporting requirements as you pointed out and under which he is currently cruising. (inconvenience versus no tax). However, if he decides to import & register it in the USA he will be subject to tax and duty but escapes the inconvenience of having to leave the country for 15days every year by putting on his US citizen hat.
I believe the latter is his best solution, he can take advantage of the favourable cruising permit
granted US citizens and there should be no duty if it is a NAFTA vessel. As well, he is already in Delaware so there is no State tax.