sentences:  The two countries quickly established diplomatic relations, with Joel Poinsett as the first envoy.In 1828 Mexico and the United States confirmed the boundaries established by the Adams–Onís Treaty by concluding the Treaty of Limits, but certain elements in the United States were greatly displeased with the treaty, as it relinquished rights to Texas.Poinsett, a supporter of the Monroe Doctrine, was convinced that republicanism was the only acceptable form of government for all countries in the Americas, and tried to influence the government of Agustín de Iturbide, which was beginning to show signs of weakness and divisiveness.