I'm not sure I can answer your specific question, but I worry that you're not prepared for how many weird cross-border issues exist.
A couple questions:
1) have you been living in Canada for a while, and how long do you plan to stay?
2) do you have canadian bank accounts or investment accounts in Canada? (if so, do they hold Canadian mutual funds, GICs, or ETFs?)
3) do you have US investment accounts? (if so, do they contain US mutual funds?)
4) are you aware of FATCA restrictions on investing as a US citizen outside of the US, and FBAR reporting requirements, and have you been compliant with them?
If the answers include yes to #2 or #3, and no to #4 - start worrying. You will need to do some catch-up and get into compliance once you are aware of the rules. If breaking the rules was minor and purely due to ignorance, you will likely just catch-up on reporting, potentially divest some assets, and won't see any penalties.
I have a lot of info and links for you if you have follow-up questions. The book: "The American in Canada" is also a great primer, especially if you have just moved.
For your specific questions...
I believe discover is saying the same thing as Capital One: "because I am a US Citizen, I don't have to report US bank accounts to the US government." [Because you do have to report non-US bank accounts - aka the FBAR]
And for addresses, you will pretty much have to use your US address for US bank signups - but if they find out it's not your residential address they may close the account (this include investment accounts) due to FATCA hassles.
As an American who doesn't live in the US - welcome to second class citizenship.