An interesting but obscure PoD would be the
Venezuelan Crisis of 1902-'03, which could lead to a war with the United States opposed by Britain, Germany and Italy. At this point the US Army is tiny and the Royal Navy by itself can squash the US Navy like a bug, even withough help from the German navy. The question then is whether the Anglo-German-Italian alliance can reinforce Canada and other British possessions at risk quicker than the Americans can raise an army to invade them with. Being faced with the world's largest navy and the world's most professional arm, there definitely is potential for an American defeat.
Another possibility it the
Venezuelan crisis of 1895, pitting the United States against Great Britain as well, though this time in a one on one confrontation. The unquestionable advantage of the Royal Navy remains, though the British Army too is quite small.