The NYT on the detained tourists I've been writing about: https://www.nytimes.com/2025/03/13/world/europe/german-tourists-detained-deported.html.  Better late than never.  The German woman is now back in Germany, but the Welsh tourist is still in detention, AFAIK.  I called the UK Embassy in San Francisco, but they are unable to give out information on British nationals due to privacy constraints.  I called the ICE number for verification of detention, but the voicemail system I was directed to was full and not accepting more messages.

Update on the update: the letter I sent to the Welsh woman in detention in Tacoma was returned with the words "Not Here" handwritten on the envelope.  Looks like she was released to return home after three weeks in a cell.

If you don't have a US passport, you should not travel to the US at present.  Detention is cruel and unpleasant, and for an indeterminate length of time.  This warning should be posted as a travel advisory on other countries' government web sites.