I've sometimes speculated about an alternative history in which some sentry on the Heights of Abraham spotted the British climbing up to attack, because sopmeone sneezes, and he gives the alarm.

French victory in the battle leads to an end of the war in which Canada stays French, the Thirteen Colonies stay British. No revolution, because the British are seen as a valuable protection against the French, and the taxes don't seem such a bad price to pay for it.

A generation later the French have consolidated from Louisiana to Canada, in partnership with the existing inmhabitants, and have probably broken off from the France, where there hasn't been a French Revolution, which had largely been precipitated by defeat in the Seven Years War. And so forth.

All because of a sneeze. Alternative history is great stuff.