It was poor wording on my part! With conditions, the Canadian and US experience requirements can be satisfied by flight training received from foreign instructors. Here is an example from the Canadian regulations that bears relevance to the OP's ambitions:
421.38 Requirements
(1) Seaplane Rating - Requirements
...
(d) Credits for Foreign Applicants
The holder of a pilot licence - aeroplane category, issued by a
Contracting State, shall be deemed to have met the seaplane training
requirements specified above, provided that the applicant:
(i) has completed a minimum of 50 hours flight time as
pilot-in-command in seaplanes during the 12 months preceding the date
of application for the rating, or
(ii) has met the prescribed standards of the State concerned, to act
as pilot-in-command of seaplanes during the 12 months preceding the
date of application for the rating.
Considering this rule, it might be worthwhile for the OP to do an EASA SEP (Sea) class rating. Were it the OP's intention to convert the Canadian licence/ratings to the US equivalent at some future point, in accordance with the US–Canada conversion agreement, then the Canadian SES class rating would not be eligible for conversion because the rating would not have been gained by way of a Canadian skill test. That is what is meant by "issued on the basis of a foreign license (sic)."
Transport Canada will also grant a (restricted) PPL to an ICAO PPL holder, who meets certain conditions, without a Canadian skill test being done. The licence will bear an annotation to the effect that it was issued on the basis of a foreign licence, being removed only upon completion of the skill test. Above I mentioned that OP could apply for a Foreign Licence Validation Certificate should any PIC flying on a Canadian aeroplane be necessary. However, the FLVC cannot be granted to persons who reside in Canada, in which case the (restricted) PPL can provide a temporary solution.