Flag of the United Colonies, 1776; and flag of the United States, 1776-1777.
The canton shows the flag of Britain that had been in use since 1606 (see here: Rippled Flag Britain 1606-1801) and had thirteen stripes representing the thirteen colonies of the United Colonies and later the thirteen states of the United States.
Note: I use a standard palette of shades of colours for the flag designs. Contrary to the images of flags depicted on Wikipedia, I do not follow the "official" shades of colours claimed by governments as well as alternate history flags based on flags of existing countries. The problem is that it commonly results in bizarre shading of a flag if they are taken literally - in practice such "official" colour shades are almost never applied and standard reds, blues, etc, are used.