Lol I don't know how people keep track of all these credit cards. I only have three accounts, and have had them since the early 80s. (Actually the PC Mastercard I opened in 2000-something)
To the OP.. Don't cancel your Canadian credit cards.. When I worked [I never officially established a residence] in the US, I relied solely on my Canadian cards (more specifically, my AMEX). If your intention is to return to Canada, don't cancel the cards.. You can do business in the US just fine... Many banks cater to Canadians (RBC, Harris, and TD are some)..