A logging question

Hi all. I've been reading this group for a while, but this is my first
post here.

I have a US PPL, and I travel to Montreal frequently on business. I went
over to the Montreal Flying Club at St. Hubert last week to see about
flying in Canada. Evidently, under reciprocal agreements, I can easily
get a Canadian license. Basically all I need are a Canadian medical and
a short written test.

While I was there, I made a short flight up the St. Lawrence with one of
their instructors. I did all the flying, but I have logged it as dual,
but of course the tail number is a "C-....". The question is, what are
the rules regarding the time logged under a foreign license? Can it be
applied for requirements for advanced ratings on the US side? Or does
time in a "C-...." only apply for Canadian ratings?

Also, if I were to get a Canadian license, then a seaplane rating on it,
for example, would the seaplane rating apply for my US license? Can I
get both upgraded at the same time?

By the way, if you are ever in Montreal, I can highly recommend a stop
by the Montreal Flying Club at St. Hubert airport on the south shore.
Very nice folks and very well maintained aircraft. Also a very nice
little airport.

Regards,
Austin