Complex sentence: State visits are visits to the United States led by a foreign head of state acting in his or her official capacity as the sovereign and embodiment of the state itself and are, therefore, described as the "visit of (name of state)".
Split into simpler sentences: State visits are visits to the United States led by a foreign head of state acting in his or her sovereign capacity and as the embodiment of the state itself. They are, therefore, described as the "visit of (name of state)".