[michaelmrose]

A hostile foreign power has access to millions to billions of its own citizens and a tiny number of agents who are US citizens because of the comparative difficulty in acquiring agents because such a situation is risky for both parties.

Given substantial financial resources like a state actor getting that person to naturalized status seems relatively trivial.

It may simultaneously be true that on average natural and naturalized citizens are equally loyal, moral, and trustworthy and naturalized citizens in sensitive areas are a risk because it makes it easier for foreign powers to infiltrate you because of the comparative difficulty of acquiring the services of a natural born citizen.