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.
You know, I have been a digital nomad before it was cool, around 2006-2008. And what I learned is the world is simply behind legislation wise and it is us who needs to adjust. Indeed, these days one could use a different visa created for this purpose every year from [dozens of countries](https://travel.stackexchange.com/a/158462/4188) and never have a residence -- or so it seems.

What I am leading to is this: we need to construct a narrative that is plausible, easily acceptable by authorities and somewhat defensible by us legally. Our realities simply do not fit the legislation. It's severely behind. Do not fret too much just make sure you can make an argument if push comes to shove. Example: do you need to file a tax return this year in Germany? Great, you are a German resident.