It's not about the parent (which is not a job by the way). We are talking about actual people turning 21 and having no choice but to leave the country where they spend their whole life based on the situation of a different person. I personally have difficulty thinking of a more unfair situation.

Note that the USA is pretty exceptional in this regard. Most countries don't ask for people to be permanent resident before being able to apply for naturalization and children of immigrant having lived their whole life in a country can just apply for and be granted citizenship.

If it helps, you're arguing a different point than I am. I agree the rules are bad, the child should be able to stay. However, the parents don't get to lay the entire blame on the government/laws, because they knew going into the situation what was going to happen. They _chose_ to set things up so their child would be sent back to a country it didn't know.