Can the War of 1812 turn into a fight to the finish?

  Well baring major disaster in Europe the US isn't going to drive the UK out of the Caribbean.  It lacks the power to stand up to the RN and the colonies there are too damned important at this stage.   Also provided Britain can hold on until Napoleon is defeated, which is very likely once he slaughters his army in Russia, its unlikely that Canada will fall.  Again the RN means reinforcement is fairly easy once troops are available and also the region is pretty well buffered by the Indians in the west and New England, which bitterly opposed the war in the east.  Plus for most of the OTL war the American army was fairly limited with many limitations, especially with the militia units used and they were also attacking other Indians in the south.

  Having the US seriously trashed would be fairly easy.  Plenty of POD here, including:

a)  Isaac_Brock doesn't die in 1812 as he seemed to be very good at leading the Canadians and working with Tecumseh

b)  Something, say some greater British successes in the west meaning it holds a lot of 'American' territory or possibly Napoleon has more success in the 100 Days, which prompts the US to continue the war, means it goes on longer this could result in:

i)  Growing unrest in the New England area prompts the Hartford_Convention to escalate into a decision to secede. 

ii)  Britain moblises more forces to punish the US, with the war against Napoleon over and makes more raids on the US coast, possibly also getting a lodgement in the south and encouraging slaves to defect to Britain in return for freedom.

iii)  If the war goes into 1816 then you have the Year_Without_a_Summer, which will hurt everybody but probably be seriously crippling for the US war effort, as it will face a lot of problems and due to blockade not be able to look elsewhere for supplies, food, etc. 

  Also there might be plenty of other butterflies that could have effect.  I once planned a TL with a POD in Jan 1809 - i.e. Sir John Moore doesn't die at Corunna and along with some of the other points above Britain gains most of the old NW territories - i.e. the area between the Ohio and upper Mississippi rivers west of Ohio state as an Indian protectorate, plus a campaign in the south leaving Britain with Florida as a homeland for Indian and escaped slave allies while the NE states have seceded with support from Britain after their attacked by the US so they end up as allies.  As part of this the border westwards could easily be say on the 45th parallel.

  Of course any significant changes which sees the US lose territory could set up problems of a later war, but this is likely to be bad for the US while major losses in the north could leave a US dominated, at least in the Senate, by slave states, especially if you have both the loss of the NW territories and the New England states.  This wouldn't immediately leave the US restricted to east of the Mississippi, although until after 1814 I think Britain never recognised the forced sale of Louisiana from Spain to France and hence its later sale to the US.  Or the impact of later events could mean they lose most/all of their lands west of the river.

  Not while Napoleon is a threat that's true.  However by the time the war starts he's already committed to the invasion of Russia which is always likely to end badly and could have gone much worse for him personally.  Also the pressure against French domination was growing so he probably has limited time left under just about any circumstances. 

  OTL it was relatively easy to get a return to the pre-war status quo as neither side had any significant territorial gains, the US realised they couldn't face an undistracted UK and the UK after over two decades of war wanted peace.  However if say the US had gained a sizeable section of Canada and tried to keep it, or Britain [and its Indian allies] still held much of the 'old NW' area and Britain argued for maintaining a protectorate there the war could have gone on longer and seen markedly more damage, especially on the US side.

  Note I'm not talking of anything impracticable like Britain reconquering the entire US.  However I could see the bulk of the NW territories being lost, with a carry on impact on the border west to the Pacific and an independent New England nation.  Which would have big impacts on the development of the US and Canada, especially if bad relations continued.