So the bigger question: why does the US allow dual citizenship at all? No, bub.
The bigger question is "Why not allow dual citizenship?" What's the harm?
You've got the burden of proof that there's something nefarious about it.
Not nefarious. But it forces people to choose between the US and the land they may call home, and it is an unfair burden to place on people.
What's the harm? Maybe it's not useful (from a purely US point of view) to have Mexican's crossing our border, voting in our elections solely with an eye towards how the US can funnel more assistance to Mexico as some have suggested happens. Maybe it isn't useful for the US to give Israel a pass when they send controlled US technology to China solely because Jewish Americans are perceived to be willing to back Israel even when it works against US interests.
Sorry, bub. The burden of proof, IMHO, should be on those who'll tolerate those involved in the US political process who aren't clearly prepared to place the interests of the US first.