Alternate history speculation is a fool's game, but a fun one. ;) It's also extremely likely that the (states that make up the) United States would be the territory of other powers if it hadn't united.

It's interesting to speculate on how much of the colonies Britain would have won back in the War of 1812 if it hadn't faced a unified front, or what a powerful France would have done in world history if it had never made the Louisiana purchase sale to the United States because there would have been no United States to make the sale to (or, for that matter, what a powerful Spain would have done if France had made the sale to Spain instead, expanding the Mexican holdings). Or how long slavery would have lasted in North America if there had been no pressure of maintaining a national-scale rule of law to bring disagreements between Northern and Southern states to the point of a military conflict.