In a world in which it stays out of the Great War of 1914, the United States would follow two possible paths. One would see the United States eschew overseas entanglements. The other would involve a great deal of involvement in the Pacific and the Caribbean.
The point of departure for the first point might be a decision, on the part of
William Jennings Bryant, to oppose the war against Spain. (In our timeline, Bryant was an enthusiastic supporter of the war and yet, soon thereafter, an opponent of the territorial acquisitions that followed.) This might lead to a situation in which the US refrained from building the Panama Canal, thereby increasing the demand for railroads that connected the Pacific Coast with other parts of the Continental United States. That, in turn, might lead to increased trade with Canada, as Americans made greater use of the Canadian Pacific Railway to move goods across the Empty Quarter.
The point of departure for the second path might be something that prevented US entry in the Great War of 1914. This might include big decisions (such as a German decision to replace the Schlieffen/Moltke plan with a "defend in the west, attack in the east" deployment) or small events (such as those which would prevent the sinking of the Lusitania.) In such a situation, the United States might continue with the sort of interventions and expansions that took place in our time line in the years between 1898 and 1917. This, in turn, might lead to an earlier conflict with Japan.
As both of these paths would keep the United States out of the Great War of 1914, they would result in a situation in which that war would have ended soon after the collapse of the Russian Empire, and thus, no later than the spring or summer of 1917. This would leave the British Empire in a much stronger position, whether in terms of leadership talent, money, or morale. That, in turn, would reduce, rather than increase, the chances of the acquisition, by the United States, of Canadian territories.
