Should be, but rarely are. The 1965 immigration law has been a disaster, filling the United States with people who have no desire to assimilate and who remain loyal to the cultures from which they came.
The greatest harm is the numbers - that each wasn’t just sprinkled through and thus left to assimilate but in large enough numbers to congregate, create enclaves, resist assimilation.
Thus you had the Armenian quarter in Jerusalem for centuries, China-towns that have lasted 100-200 years, etc.