How did the weakness of the Articles of Confederation affect relations with other nations?

The Articles of Confederation diffused governmental power greatly, essentially making the federal government ineffective in many areas, including the power to tax the states and foreign relations. It emphasized the power of the states over the federal government, and thus weakened the federal government in large part. Because the Articles did not give the federal government enough authority, it had great difficulty negotiating and enforcing foreign relations.

The Articles gave the power of foreign relations to the federal government, and established a Department of Foreign Affairs in 1871; however, the Articles did not specifically ban the states from conducting their own relations with foreign countries. This proved to be a problem early on, when Georgia attempted to pursue its own foreign policy with Spanish Florida. Georgia tried to gain land by occupying disputed territories, and also threatened to wage war against Spanish Florida if Spain did not attempt to stop Native American attacks and stop harboring escaped slaves from Georgia. Spain also demanded that the U.S. stop using the Mississippi river, and U.S. claims to use land west of the Allegheny mountains. Because the Articles required 2/3rds of the states to ratify any treaty negotiated by Congress/U.S. diplomats, and because the Southern states opposed the compromise negotiated in the treaty, the U.S. was unable to ratify a treaty with Spain over the matter. Negotiations had to be suspended until the Constitution created a stronger federal government with the power to negotiate and enforce such treaties. Many states also began implementing tariffs on Great Britain, or banning British ships from doing trade in their states altogether. The states refused to allow the federal government control to regulate trade because of their fear of an overly controlling central government. As a result, the U.S. could not implement navigation acts to control trade with Great Britain, and Britain dominated the U.S. in the area of trade.

The Longchamps Affair illustrated the inability of the federal government to negotiate foreign affairs. A former soldier and a French citizen, Longchamps was accused of assaulting the French Minister to the U.S. France demanded that the U.S. extradite Longchamps for trial in France. Pennsylvania, the state where the incident occurred, refused to extradite Longchamps, insisting that Pennsylvania had jurisdiction over the matter, because there was no treaty between the U.S. and France concerning these types of incidents. Thus, an issue that should have been dealt with by the federal government was commandeered by the state of Pennsylvania, causing difficulties with the French government as a result. 

Because of the weakness of the federal government, the U.S. was unable to defend its interests abroad. This caused many issues with pirates, who attacked American ships, which had no protection abroad. Additionally, Algiers declared war on the U.S. in 1785, capturing two U.S. ships and holding the crews for ransom. Congress, due to its inability to force states to pay taxes to the federal government, could not afford the ransom the Algerians demanded. The U.S. could not create a treaty for peace with Algiers, nor raise the money to free the prisoners, until 1796, after the Constitution was established. 

The Articles gave Congress the power to negotiate treaties, but not to enforce them. Thus, there were issues with the enforcement of the Treaty of Paris (1873), which ended the Revolutionary War. The treaty specified that the British must remove all military personnel from U.S. soil. The British did not do so, as a result of disputes, and Congress had no power to enforce the measure. The inability to make the British leave caused problems with the Native Americans, who saw the new government as weak and ineffective. Also, the treaty allowed British creditors to sue U.S. citizens for debts compiled before the Revolutionary War. Obviously, this second measure was very unpopular in the U.S., and many states refused to enforce it. The U.S. also did not return confiscated land and property to British loyalists after the war. As a result of this refusal, the British continued to occupy some military forts in the U.S.

The problems caused with foreign relations were a direct result of the Articles of Confederation not granting enough power to the federal government. The Constitution corrected these oversights.