Final answer:
The two fatal flaws of the Articles of Confederation were its inability to tax and raise a military, leading to financial and defense problems which culminated in Shays's Rebellion and ultimately the formation of a new Constitution.
Step-by-step explanation:
The two fatal flaws of the Articles of Confederation were primarily the lack of power given to the national government to independently tax and raise a military. The national government could not compel the states to pay their share of the Revolutionary War debt or impose tariffs to raise funds, crippling its financial capabilities. Moreover, it could not effectively defend the nation, as seen during events like Shays's Rebellion, where it lacked the power to raise an army and had to rely on state militias.
This led to a realization that a stronger federal government was necessary, eventually resulting in the Constitutional Convention and the creation of a new Constitution. The Articles of Confederation had succeeded in maintaining state sovereignty, but at the cost of a central government too weak to deal with the United States' economic and defense needs, thus confirming the need for a stronger centralized authority.