Smaug

I got a phone call from my family in the UK today that my mother's health is failing. She has dementia and is entering final stages. They cannot do tests or give an estimate of how long she might live for. Days, weeks, possibly months. They are talking about withholding medication to let nature take its course. I doubt I will easily be able to get a medical professional to sign a document, since it's extremely difficult to even get her doctor's office to answer the phone.

I am a naturalized US Citizen, with no US passport. I have a valid British passport, and I have my naturalization certificate original.

I was planning on doing an expedited passport request, and going in-person to the Charlotte, NC passport office since they accept walk-ins without appts.

If I don't get the passport back in time for the flight to the UK, I can still travel on my UK passport.

However, if I fly back home without a US passport, what will happen when I try to re-enter the US? Since I'm a US citizen, I expect they'd have to admit me, but could I technically enter the US with my UK passport? If so, what do I say?

I still need to arrange my flight time, and have to consider family/work/costs of flights/availability of people to pick me up from the airport, so I don't know when I am able to travel.

BritInParis

Legally you need to enter and exit the US on a US passport. Practically speaking you are likely to be able to travel to the UK without one but you'll have trouble getting back to the US as you'll either need an ESTA or a visa and as a US citizen you won't be eligible for either.

If you haven't booked your flight yet, or even know when it is likely to be, then I would get your US passport first. You don't want any additional worries.

Rete

If you walk into the Passport Office with the completed form and your imminent confirmed travel itinerary, you can walk out with the US Passport on the same day as you apply for expedited service. The fee for the US Passport is $110 and the fee for expediting it is $60. I had to do this 10 days ago for my upcoming trip when I discovered my passport had disappeared from my desk. They say expedition is from 1 to 7 days. I used a service as my closest passport office is in New Orleans and that is around trip of 4 hours. They had my forms, evidence and check on a Wednesday, took it to the Passport Office on Thursday and I had it in my hands on Monday.

As for appointments not being needed, the Nola office said if you didn't have an appointment to get there first thing in the morning before the office even opens as they only allow so many non-appointments in per day.

Good luck and so sorry to hear your news on your mother's health.