This rapid population growth comes from the arrival of immigrants and from their much higher birth rates. At the turn of the century our population grew regardless of immigration because natives also had large families. This means that immigration has become the determinate factor in population growth. None of this is to say that we should stop accepting immigrants altogether. But it does suggest that lowering the overall level of immigration and selecting more immigrants based on needed skills, instead of the current system where 70 percent of immigrants are admitted because they have relatives in the United States, would make a good deal of sense.
Most policies have to change with the times, and immigration policy is no exception.