Technically the US has already, over two subsequent administrations intentionally and with a handful of discrete attacks, gone after and killed a father, his US citizen son (a minor), and US citizen daughter (a minor) in a series of targeted missile and commando strikes. It was done outside US soil but it was at least one targeted killings of US citizen kid. The daughter may have been accidental since her assassination was a commando raid and not two seperate drone strikes like they used to get the son.