Fun fact, the vast majority of Canadian population live more southern than anywhere in Ireland, James Bay (southernmost point of Hudson's Bay) shares roughly the same latitude with Co. Cork.
No — thuaidh i gCeanada is in reference to the speaker, not in reference to Canada. “In northern Canada” would be i dtuaisceart Cheanada (literally “in (the) north of Canada”; this is an expression where English needs an article and Irish doesn’t).