Upvote:3
Probably segregating people at a stop would be a logistical nightmare for airport staff.
That's called "transit" and that is unfortunately a concept the US and Canada don't have.
For the most part connecting in the US has the same requirements as entering the US. There may be exceptions but this depends a lot on your specific details and may take considerable effort to research and track: Covid related rules do change fast. It would be safest to assume that have to meet the same requirements as for entry into the US.