Consider this scenario: an immigrant family is denied entry into the u. s. based solely on their country of origin, while other families are allowed entry because the u. s. has no restrictions on immigration from some countries. this was common in the u. s. until the immigration and nationality act of 1965 did what?

It basically completely restructured US immigration policy. No longer was the system based on a quota system, where only a limited number of people were allowed to come from certain countries.
Instead, immigration policy became focused on helping reunite families. There was also the fact that we wanted skilled laborers to come, so we started accepting people based on their skills and professions.