Answer:
The historical event that explains the large number of refugees to the United States arriving from Bosnia-Herzegovina, Serbia, and Montenegro from 1999 to 2001 was the Yugoslav Wars.
Step-by-step explanation:
The Yugoslav Wars were a series of armed conflicts between 1991 and 2001 in the territory of the former Yugoslavia, which led to the collapse of the country.
The wars were characterized by bitter ethnic conflicts between population groups in former Yugoslavia. The conflicts had various political, cultural and ethnic undertones, not least the fear of Serbian domination. The wars were among the bloodiest in Europe since World War II, resulting in 300,000 dead and millions of refugees. They were also the first conflicts since World War II, formally referred to as genocide. Several of the parties involved have been charged with war crimes.