Final answer:
The 'Critical Period' from 1781 to 1789 was a time of intense diplomatic and financial challenges for the United States under the Articles of Confederation. The young nation struggled with foreign relations, national debt, and internal governance, highlighting the need for a stronger national government and financial system.
Step-by-step explanation:
The "Critical Period" refers to a pivotal time in American history, specifically from 1781 to 1789, when the Articles of Confederation were in effect. John Quincy Adams named this era as such due to the significant difficulties faced by the young nation. These challenges included diplomatic and financial struggles, such as the need for a national bank, the power to issue government bonds and levy taxes, and difficulties in coping with foreign relations and the nation's war-related debt.
Despite the resumption of trade and opening of new markets, the weak national government was burdened with fiscal woes and foreign governments perceived the United States as feeble. Many Americans had expected a smooth transition from British colonies to an independent nation, but these expectations were unrealistic, which led to numerous internal problems and a skepticism from other nations toward the U.S.