In the US, private pilots flying under VFR are implicitly allowed to fly without visual reference to the ground, eg. over an overcast cloud layer, as long as they maintain appropriate VFR weather minimums. The same is true for flying VFR at night.
In Canada, a separate add-on "VFR OTT" rating is required in order to operate "over the top", and there's also an add-on rating for flying VFR at night.
US pilots can operate Canadian-registered aircraft through a Foreign License Validation Certificate, which as far as I can tell confers the privileges of one's native certificate. According to the ICAO, "certificates of competency and licenses issued or rendered valid by the contracting State in which the aircraft is registered, shall be recognized as valid by the other contracting States".
So the question is: do US pilots operating Canadian-registered aircraft via a FLVC need additional ratings to fly VFR over-the-top or at night in Canada, or are the inherent privileges of their US pilot certificate extended to Canada as well?