Okay, this is embarrassing.
There used to be an organisation with the name “Protestants and Other Americans United for Separation of Church and State.”
Later on they switched to the more diplomatic “Americans United for Separation of Church and State.”
And in more recent years they’ve informally shortened it to “Americans United.”
And until today I had them mixed up with “Citizens United.” (Or, more precisely, I had “Citizens United” mixed up with them.)
D’oh!