Can I still use my old passport if I just became a US citizen?
The United States will not require you to surrender your passport from your native country when you naturalize. However, some countries will not allow you to keep your passport when you apply to become a U.S. citizen.
People Also Ask
No, a Certificate of Naturalization cannot be used as a U.S. passport for international air travel. While a Certificate of Naturalization serves as proof of U.S. citizenship, it is not a travel document and cannot be used in place of a passport. To travel internationally, a U.S. citizen must have a valid U.S. passport.
There are no penalties. The customs officials might be furious but the only thing they can do is confirm you're citizen and let you back in. As for leaving the US, the US doesn't have exit checkpoints so you can leave on any passport.