... frustrations with how independence had led to situations where caudillos (authoritarian leaders) rose to power.
Bolivar had wanted a united Spanish America, a great nations, but the wars of independence had tended to result in charismatic military rulers leading their own countries in authoritarian ways -- what we today would call dictators.
Article II, Section 2 of the Constitution declares that the president "shall have Power, by and with the Advice and Consent of the Senate, to make Treaties, provided two thirds of the Senators present concur." But it doesn't say anything about the power to break treaties.