Can one really even 'stand by' for an International flight?

Flying to/from the US from another country, once it hits T-45 the flight is closed the manifest and APIS data (passport info / nationality, etc) is transmitted to the US (and other governments) Even airline employee nonevs can't fill the seat if there is a last minute no-show or a voluntary/involuntary passenger offload. I assumed the same would be in place to/from Canada.. But of course I defer to the road warriors on here to clarify!