You may be interested in this previous answer of mine which provides answers province by province about why the Canadians did not join the Thirteen Colonies. This is actually quite a popular question in this sub and there are some shorter answers in the FAQ. You may also want to do further reading here which has links to various answers compiler by /u/Master_Gunner, as well as here where u/idrymalogist provides further information.

Briefly, all the Canadian provinces except Quebec had pretty tiny populations, often only seasonal or else non-permanent, and mostly recently resettled. They had more to lose and less to gain from a revolt than did the Thirteen Colonies. Quebec had more reason to revolt, but the threat of revolution was successfully neutralized there by the British through the Quebec Act enacted by Parliament in 1774.

That said, there were Quebecoise and Nova Scotians who did fight on both sides of the war. The American Patriots made an early bid to capture Nova Scotia, but lost, and upon the loss the fervent Patriots in that colony were forced to leave, thus ending any serious Patriot threat in that colony. In Quebec, the Patriots raised two regiments that fought on the side of the Americans.

Both provinces also raised troops for the British side. About 500 men enlisted in the Royal Nova Scotia Regiment, and in Quebec, there was the Quebec City Militia as well as the Quebec (provincial) Militia who fought on the side of the British. I can't find exact numbers at the moment for either militia, but it was in the hundreds if not quite a thousand troops as well.

In both cases, these Loyalists regiments spent the war years protecting their local homeland. The Royal Nova Scotians spent most of the war in Halifax, offering support services to the British Royal Navy that used the city's ports as a base for attack along the Atlantic seaboard, especially before the capture of New York City. These same men were many of the same men that had successfully defended the colony from capture by the Americans during the Battle of Fort Cumberland.

It was largely the same in Quebec. The militia troops there defended the province from the Americans at the Battle of Quebec in 1775, and spent the remainder of the war stationed in Quebec and Montreal to defend against possible attacks.

The other provinces didn't really have enough of a population to warrant any large scale attacks or engagements, though there were some raids. For further information, see my previous response linked at the top of this post.