According to the textbook, one of the key reasons that immigration continues to be a controversial issue in the United States is because:

It is still a controversial issue because: Immigration commes with cultural diversity and this rases cultural changes.

Explanation:

Immigration is still controversial because not everyone is open to the diversity and the changes that a new culture brings. Often what is different creates uncertainty and people prefer to stay with what they think is familiar or what they are use to. Social and cultural diversity means the acceptance of what is different from once culture, this generates controverial issues.