if interview will be there obviously would not be in Ottawa.
so it should be in one of the visa offices here- LA, Seattle, New York, Detroit
it doesnt matter whether you are the permanent resident or citizen of US when filing for spousal sponsorship of Canada
the thing matters is you are the applicant who is filing from US. as Buffalo office is closed so Ottawa is doing everything and if interview comes up then the applicant cannot go to Ottawa then they have think of the visa office near your location
I hope there would be no interview for me