The primary focus of diplomatic activity during the Adams administration was a contest with Britain over trade and influence in Latin America. The United States suffered two embarrassments, one in Mexico in the Poinsett affair and the other at the Panama Congress of 1826.
The Poinsett Affair. Joel R. Poinsett of South Carolina was appointed the first American minister to newly independent Mexico, serving from 1825 to 1829. Poinsett, a capable man, exceeded his authority and became embroiled in Mexican politics, particularly in a bitter rivalry between competing rites of Freemasonry. Mexico was badly divided and armed confrontation ensued. Poinsett was eventually recalled to Washington.
The significance of that event was that it diminished the prestige of the United States in Mexican eyes while the British gained favor.
(Poinsett returned home from Mexico with cuttings of a red flowering plant that became extremely popular and later bore his name: Poinsettia pulcherrima.)
The Panama Congress (1826). Several of the newly independent Latin American republics planned to convene in Panama. Adams was anxious to send delegates to promote trade with the region, but also hoped to dissuade the new republics from attempting to liberate Cuba and Puerto Rico (both still Spanish colonies).
The Senate was reluctant. Jacksonian forces were averse to anything that would enhance the administration's public image, and some Southern senators objected to sending delegates who would serve on an equal basis with dark-skinned representatives from other nations. Because of this foot dragging, the American delegates did not arrive in Panama until after the Congress had adjourned. Britain's delegates were in session, which increased their nation's trade prospects and prestige.