This site won't allow me to post links to the relevant documents, so all I can do is point you in their general direction.
The US and Canada have what is known as a "totalization agreement". If you search for the term "us canada totalization agreement" you will find links for both the Social Security Administration (www-dot-ssa-dot-gov-whack-international-whack-Agreement_Pamphlets-whack-canada-dot-html) and Service Canada (www-dot-servicecanada-dot-gc-dot-ca-whack-eng-whack-isp-whack-ibfa-whack-countries-whack-overview-whack-usa-dot-shtml)
Basically, you will get credit from the system where you retire for the contributions to the system where you worked, but you don't need to "do anything" until you file for CPP (Canada) or Social Security (USA).