Question: Since this year, 2022, I am not a resident of Germany anymore. I am officially unregistered, and I haven't visited my home country since then. That doesn't mean that I gave up citizenship, however. I still have my German passport.

On Monday, I've a flight with transit through the US. United Airlines asks me for travel documents, and that involves entering a country of residence:

[![Screenshot of United web form](https://i.stack.imgur.com/z5Cf7.png)](https://i.stack.imgur.com/z5Cf7.png)

I don't have a country of residence. *What should I do? Can I even transit through the US?*

A United agent suggested that I contact the German embassy. It is weekend, though, and both the German as well as the American embassy are not available.

Update
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In the end, I arrived at my destination without a problem, and I did use my layover in the US to leave the airport for a night. What country I specified as country of residence, I forgot, because I couldn't edit or see it anymore after I advanced in the form. I was asked for the country of residence when I got my tickets for the connecting flight. In that case, I specified France, no problem.

Answer: 
Based on the information in your question and in the comments, you are a resident of **Germany** for US immigration purposes. The US does not have a system equivalent to the German official residence registration and does not care about your *Abmeldung*. If you are a citizen of Germany, lived there relatively recently, and are not a permanent resident of any other country, you should choose Germany as your residence and, without lying, leave border officials with the impression that you have a plan to return there.

If you make yourself appear "interesting" to border officials, perhaps by insisting that you have no residence and no definitive plan to live anywhere, you will very much increase your chances of your entry to the US being delayed or denied.
I'm adding this as an answer of what not to do, because you might not be aware of some fringe political/legal arguments people try to make in the US. There are people that refer to themselves as "Sovereign Citizens" and they talk about not being under the jurisdiction of any country's laws so they can do things such as "freely travel" or "non-commercially transit" the country without a need for driver's licenses, license plates on vehicles, etc. Basically they claim to be outside of the laws for any given city or state because they are their own country (or something like that).

This falls under the heading of "conspiracy theories" and if you want to research it, keep in mind that no legal entity in the US agrees with what they claim.

So, why bring it up? Well if you start telling officials that you don't have a country of residency/jurisdiction and you should be free to travel, etc, you're using some common phrases that might lump you in with this movement. It's the first thing I thought of when you said "you're not a resident of any country", but I'm probably biased from watching several videos about the sovereign citizen movement.

So, I agree with the other answers saying what you should do, but don't go around saying you're not a resident of any country without a little more explanation.