Canada is the pretty, polite giant: Banff and Jasper looking like a desktop wallpaper, Vancouver wedged between ocean and mountains, Toronto's neighborhoods, Montréal's terrasses, and a lot of empty, beautiful space in between. The cities are easy. The wilderness is the point, and it is farther away than the map suggests.
Distances are the first-timer tax. Toronto to Vancouver is a four-hour flight, not a cute train day. Pick a region — the Rockies, the east-coast cities, or British Columbia — and fly the long hops. Trying to 'do Canada' in two weeks is how you see airports.
Summer is lakes and long evenings. Winter is a different country: serious cold, serious skiing, and a Montréal that somehow still has a nightlife. Shoulder seasons are the secret, especially in the mountain parks when the larch turns and the crowds thin.
Eat poutine properly, order the all-dressed bagel in Montréal, and take the national-park boardwalks slowly. Canada is friendly without being loud about it. Give it room and it gives it back.