Why bother to renounce a citizenship which is dormant anyway? It sounds as if you are in the enviable position of being forever off the US radar until such time as you might want to exercise it. No point in burning bridges that don't have to be burned. Who knows what you might want to do in twenty years time.
Renunciations are not easy, cost money, and set you up for at least five years of back returns and FBAR. A renunciation does not relieve you of your tax obligation, but it would certainly make them aware of your existence.
A Canadian passport with a Canadian birthplace is your ticket to peace of mind. My advice--let sleeping dogs lie. Don't try to fix that which is not broken! I wish I were in your situation.
(I'm not a lawyer or an accountant. I'm just a guy who is about one year into the quagmire that you can safely step around. Trust me, you don't want to go there.)
Newbie questions (do i *have* to file?)
Moderator: Mark T Serbinski CA CPA
I agree. There is no chance -- NONE -- that you will ever be "discovered" to be a US citizen, either by CBP or by IRS.
If you ever decide to retire down in US -- never say never -- then you can get compliant at that time. By then compliance will be so streamlined, that it will be do-it-yourself. If you decide to NEVER go there, then leaving this alone is your best bet.
You can bet that the current round of treaty negociations will be focused on alleviating this reporting nightmare -- it is in both countries' interest, since it generates absolutely no revenue.
If you ever decide to retire down in US -- never say never -- then you can get compliant at that time. By then compliance will be so streamlined, that it will be do-it-yourself. If you decide to NEVER go there, then leaving this alone is your best bet.
You can bet that the current round of treaty negociations will be focused on alleviating this reporting nightmare -- it is in both countries' interest, since it generates absolutely no revenue.
nelsona non grata. Non pro. Please Search previous posts, no situation is unique as you might think. Happy Browsing 
Totally agree with Maz and Nelsona. Don't bother doing anything. You are absolutely fine. Check out the Isaac Brock Society. They are all in this mess and I guarantee you that they will all agree that you are ok ignoring it. No one will come looking for you. Don't open a can of worms. I've been through it myself and you don't want to do it if you don't have to.