Answer:
A General Practititioner in the USA may belong to a Local Medical Society but it is not required. All physicians, however, must be licensed by the State in which he or she practices.
Look for (your State's name)+Medical Board. Or, call your State's Attorney General's Office and ask for the number to the State Medical Board.
All complaints to these Boards must be in writing; they do not advise you by telephone. After your written complaint, they investigate. You may or may not be informed of the outcome.