There is a lot of talk about "ooh if the Redcoats win they'd've shipped us to concentration camps after taking away our guns." Not likely; even though the Royal Navy was the finest military machine in the time, the British Army was just a glorified militia no better than our own--Patriot or Loyalist.
Perhaps I'll use my British North America TL, as people have told me it is realistic:
The most plausible POD for a Tory victory would be for Washington to be captured after a failed attack on Trenton in 1776. Howe would be free to secure the Hudson, and Burgoyne would stay in Quebec, thus preventing Saratoga. The important thing is to _NOT_ let France, Holland or Spain get in the war; else a Patriot victory is assured.
The most surprising thing about a British victory is that the Americans will win independence anyway, that the Yankees "change their government," even though George Hanover is still their head of state. This America, though, is not a federation of 13 weak States, but 4 stronger, more economically independent Dominions: New England, Pennsylvania, Virginia and Florida. The West Indies and Canada become Dominions not too long after.