Hi guys, so I did some digging on this forum and I found someone who had an agent communicate the following.. it appears that USA and Canadian address are mandatory.
-----
IMM 5406 (for Principal Applicant): The Additional Family Information (IMM 5406) is missing or incomplete. Please provide a current, completed and signed Additional Family Information (IMM 5406) for the
Principal Applicant and all dependents aged 18 and over, whether accompanying or not.
Each individual must sign their own copy of this form by hand.
Sections A, B and C must be fully completed for this form to be considered complete (Name, Marital Status, Relationship to applicant, Date of birth, Country of birth, and Address). The street number, street name, city, postal/zip code and country are
mandatory for Canada and USA addresses. All other countries must provide the City, Province/State/Parish and Country. If you are unable to provide any of the information listed above for any individual listed in section A, B and C, you must provide an explanation.
You must submit the most recent version of this form
(06-2019).
https://www.canada.ca/content/dam/ircc/migration/ircc/english/pdf/kits/forms/imm5406e.pdf
_-------