Ignoring for the sake of argument whether Britain was "successful", here are some factors to consider.
Canada was a British colony and liked it that way.
How did they handle the mostly uninhabited terrain...
It wasn't as if Britain had to storm the beaches of the United States, they'd been in North America and fighting there for a century! Most recently in the North American front of the Seven Year's War aka the French and Indian War.
They also had still had Canada. At the start of the war, Canada had 6000 regular British troops, plus its own militia. The Royal Navy was also present in Halifax with a Royal Navy Dockyard supporting the North American Station. Britain had a lot of experience in North America fighting the French.
And Canada had little interest in independence from Britain and less in joining the US. Despite the highly optimistic claims of the US war hawks, Canada was tired of US invasion attempts would strongly resist US invasion again. The first floor of the Canadian War Museum in Ottawa covers early history and can be summed up as "oh god, the Americans are going to swamp us". The Canadian War Museum has an online exhibition about each side's perspective in 1812, the US/Canada perspective is summed up in one quote...
The Americans were in high spirits, and when I said I was Canadian, one of the officers laughed and said, “You'll soon be under the Yankey government, my boy.” I was sassy, like most boys of my age, and I said, “I'm not so sure about that.”
Britain was very busy with Napoleon.
Britain had been fighting France almost continuously since 1792 starting with the War of the First Coalition against the First French Republic and ending (for our purposes) with Napoleon being sent into exile in April 1814. Napoleon would be back, but the War of 1812 would be over.
For the British, the war with the US was a side show. The overwhelming bulk of their army was fighting Napoleon and their navy was busy blockading him. War with the US was a side show until Napoleon could be dealt with.
The US army was numerous, but unreliable.
On land, the British had a strong cadre of regular troops and professional officers to draw from with years of war experience. While the US regulars were also well trained, the militias were not. Wary of a standing army, the US army relied heavily on state militias of questionable training, leadership, and equipment.
The British army was outnumbered it was bolstered with Canadians motivated to defend their homeland. While the US army had to deal with unreliable state militia wondering why they were being marched into Canada.
The US Navy was powerful, but small.
At sea, a handful of US heavy frigates, of which the 44-gun USS Constitution is a prime example, gave the smaller British frigates trouble in ship-to-ship actions.
As good as the US heavy frigates were in small battles, numerically they could not compare to even the small fraction of the Royal Navy allocated to fight America. And the US had nothing to directly challenge the British blockade, nor ships-of-the-line. As a result they had to pursue commerce raiding and blockade running rather than a conventional naval war.
The spectacular early American victories against the Royal Navy required the Royal Navy to respond. With British frigates upgunned to deal with the US heavies' "ironsides", and the full might of the Royal Navy arriving from Europe, the US Navy began to fall. USS President and Chesapeake were captured. USS United States and USS Constellation were blockaded. USS Congress was left in dock needing expensive repairs. Only USS Constitution ended the war sailing free.
The natives sided with the British.
...and the native tribes bombarding them?
It was largely the opposite. From the native perspective, the US was a threat, and the war was an opportunity to regain control of their territory. With a handful of exceptions, the natives sided with the British.
As British colonists, Britain kept the Americans in check and largely prevented them from advancing past the Appalachian Mountains into native territory. But America as an independent nation crossed those mountains and was busily encroaching on native territory.
The British saw the potential of strong native tribes in the American (Old) Northwest as a buffer against American expansion, as well as a lucrative fur trade, and supported them. Tecumseh's Confederacy and other tribes in the Northwest sided with the British.
The British and Canadians mostly fought a defensive war.
The Americans spent most of the war attempting to invade Canada, a perpetual target of early American ambitions, with some success. It was the Americans who had to march through the wilderness into Canadian territory. The British and Canadians were on the defensive.
After the war in Europe was over in 1814 and the British could spare resources for America, the British and Canadians went on the offensive. That didn't go so well either and, probably fortunately for the Americans, the war ended before the British Army could have another go.
Once Napoleon was dealt with, the war ended quickly.
Once Napoleon was, apparently, defeated, Britain could send its full might against the US. Once they did, the war deteriorated rapidly for the Americans and peace negotiations began. Ironically, one of the major stated reasons for the US declaring war, the impressment of US sailors into the Royal Navy, was now moot; with the threat of Napoleon gone the Royal Navy didn't have such a pressing need for sailors.
The US now to faced the full might of the British military. The blockade was costing the economy dearly. Their hopes for an easy victory in Canada were dashed. The primary reason for going to war was moot.
Britain had no interest in war in the first place. They were tired of over 2 decades of war, war taxes were unpopular. And while the war was going well at sea, it was not so conclusive on land. While the raid on Washington was successful it had no strategic effect. The British invasion of New York, intended to cut the US in half, was defeated at Plattsburgh.
So both sides concluded the war a draw.
