From the Department of State website:

"Potential Challenges to Holding Dual Nationality

Countries have different laws and regulations for dual nationals and some countries may not permit dual nationality. Research your destination on our Country Information Page. You should also check with the embassy of any country where you hold a foreign nationality for relevant nationality laws before travel. Examples of regulations that may impact a dual national include the following:

Entry and Exit Requirements: When traveling to a country where you have U.S. and that country’s nationality, you may be required to enter and depart on a passport from that country or present a valid identity document from that country. Some countries impose specific restrictions on departing nationals, such as the requirement for an exit visa.
Exit Bans: Countries may impose exit bans on U.S. and dual nationals for a variety of reasons, such as an alternative to criminal detention or in cases of civil or familial disputes. Exit bans may also be used coercively on individuals who are not facing criminal charges themselves, but rather to compel an associate or relative under investigation to return from abroad. Dual nationals subject to an exit ban may not know how long the restrictions or investigation may continue. Exit bans or the prolonged processing of civil documents often create a significant financial burden, including unemployment, unexpected living expenses, and fines.
Limited U.S. Assistance Abroad: Local authorities may not recognize your U.S. nationality if you are also a national of that country, especially if you did not enter the country using your U.S. passport. The U.S. embassy or consulate’s ability to provide consular assistance may be limited.
Notification and Access to Detained Dual Nationals: Many countries do not recognize dual nationality under their laws, even if they do not expressly prohibit dual nationality. U.S. consular officials may not be permitted to access U.S. nationals in detention if they are also nationals of the country where they are detained. Dual nationals who are arrested or detained should request that police or prison officials notify the closest U.S. embassy or consulate.
Military Service: Dual nationals may be subject to mandatory military service in a foreign country. This obligation may be imposed immediately upon arrival or when attempting to depart the country.
Registration: In some countries, you may be required to register your other nationalities.
Prohibition of Dual Nationality: Some countries have laws that prohibit dual nationality, and you may be forced to give up a foreign nationality. You could be compelled to do so through a formal act of renunciation. We recommend that you do research on the dual nationality laws of the countries in which you are a dual national, or where you are interested in naturalizing. You can find a list of local attorneys who may be able to assist you on the websites of U.S. embassies and consulates abroad, or travel.state.gov."

Anonymous wrote:This entire thread, and every response in it, just shows me how terribly idiotic Americans are.

Oh yay, the arrogant expat has joined us to bless us with their worldly ways.

This entire thread, and every response in it, just shows me how terribly idiotic Americans are.

Tuck and roll, OP, tuck and roll!

Or just charter a jet FFS.

When entering and leaving the US, always use the US passport (if that is one of them). Same with the other countries.

Anonymous wrote:
Anyone with multiple passports knows that even when you travel with all of them, you have all but the one you’re traveling with stashed away (and depending on the transit countries, you don’t bring extras at all!), you don’t indiscriminately show immigration officials all of them! Think of it like two having license plates from two different states on one car. It is totally suspicious to show passports from more than one country at passport control! The entire point of passport control is to figure out who is where, from where, at what time. Different countries have different arrangements with one another and by declaring what passport you are traveling with, you are operating under the rules- and protections, or lack of- of that agreement.

Also there are plenty of countries that explicitly prohibit holding multiple passports even though plenty of their citizens do so.

Wow, I only have one passport so I always wondered if dual citizenship travelers were allowed to travel with two passports and how that would work.

Anonymous wrote:These are official documents OP and the stamp means something. It’s not like getting a national park stamp in your fake NPS passport!!!

Yup, these aren’t souvenirs or Pokémon, OP. Treating them as such is just asking for trouble.