Citizenship and registration

[cheetham]

We are in the process of buying a new sailboat (Beneteau 37, with 29HP aux inboard).
I have discovered that I cannot get USCG registration as I am not a US citizen. I can get state registration (NC), but have been advised that If going offshore, it's better to have a national flag (registration). I have UK and SA citizenship. Would any fellow cruise like to advise on:

1 - is it necessary to get national registration?
2 - what are the pros/cons and hassles involved?
3 - if I only have NC registration will I have difficulty sailing/entering Bemuda, Bahamas, various carribean islands?

Have done extensive web search, and only see headaches ahead

Thanks in advance