Difference between us and ca?

(The following is asked on behalf of someone else, and their reddit acc is too new to post)

I am very new to the Amazon seller central thing and registering an account on behalf of the company I work for. Would be really appreciated if anyone can share insights of registering using company registered in different regions.

I tried to reach out to Amazon support, it is either no contact form available, or they refused to re-direct me to the correct department. I really wish to know the difference in policy/legislation and how it will impact on tax and stuff. Thank you for the help in advance!