[jjotto]

Not true.

https://travel.state.gov/content/travel/en/legal/travel-legal-considerations/Advice-about-Possible-Loss-of-US-Nationality-Dual-Nationality/Dual-Nationality.html

… U.S. law does not mention dual nationality or require a person to choose one nationality or another. A U.S. citizen may naturalize in a foreign state without any risk to his or her U.S. citizenship…

[Alberta's Child]

I’ve always understood that the U.S. doesn’t recognize dual nationality for immigrants who become U.S. citizens (that is, the foreign national must renounce their former citizenship as a condition of getting their citizenship here). Maybe that’s not the case anymore?

At any rate, the U.S. government never really had any control over dual citizenship for people who qualified as legal citizens of two different countries simply as a result of their circumstances. If you have one American parent and one Canadian parent, you’re considered a citizen of both countries without doing anything at all.