Of the main branches of the English language, Canadian English is the closest relative to American English, which, given history, makes a lot of sense: In 1607 brave men got off the boat in what is now Virginia to form the first permanent colony in North America for England and not long after that there were forays into New England and the Maritimes. Thus the foundations of the two are bound in the settlers that came from England, Scotland, Ireland, Cornwall, and Wales in the 17th century.
And then, after that, it gets tricky.
Canadian English obviously has more contact with Canadian French, itself the descendant of how people learned to parler français in the 1600s-1700s. Canadian French is the descendent of dialects and sociolects present in France before it was more standardized, which is why it has features more in common with a peasant from Poitou, Normandy, or Maine than modern bog standard French based on the Parisian dialect. When it mixes with an Anglophone substrate, weird things happen, like occasionally using French numbers for English street names, like in Quebec. When it goes in the other direction, not uncommon in Eastern Canada, the pronunciation sounds nothing like anywhere else in the world and if you want to know what this sounds like, go to Youtube and look up a boy who is trying on ballet clothes in Montreal. He is obviously bilingual but his speech sounds like what happens when you put the two dominant tongues together and threw them in a blender.Consider that he is only about nine or ten. A definite sign of evolution.
Canada was obviously more receptive to the Johnson dictionary than Webster's and to this day remains loyal to it. Bluntly the stubborn facts are that America voted itself off the island in 1776 and for a long time was disinterested in following certain trends in Europe: hence, we stil, like stubborn mules, stick to units of measurement that the British used in the 1750s for its navy and don't change to SI units unless we absolutely must lest mayhem result (scientific papers, medicine, international shipping, the army, border areas so we don't cause car crashes.) Canadian raising is a feature found in most of Canada but absent in large pockets of the US. The prairie provinces have a rounder o than their southern neighbors, like in the infamous word "hoser". Mary marry and merry are distinctly different words in all forms of Canadian English, but not in the Southeast US or some forms of black English.