From an insurance
perspective, where the boat is registered is not important. Insurance
companies care about Navigation
Territory (where you are going to use the boat), your "regular mooring
address", and what your mailing address is. To that end, having a mailing address in the USA (even if it's just a mail forwarding company, like Voyager mail forwarding) will allow you to get insurance through an American company. European Insurers will be fine with a Canadian, US, or European address.
I work with both European and US marine
insurance companies, so when you're ready for a quote on insurance, send me an off-line message. Best of luck finding your dream boat,