I'd ask the Freedom From Religion Foundation about that ... or maybe American's United for the Separation of Church and State. You might talk to American Atheists, too, while you're at it, and there are probably a couple other related outfits that don't come immediately to mind.
Are atheists utterly united? Nope ... but we have some organizations which kick ass and take tickets and have some significant notches on their gun belts ... so I wouldn't lose hope JUST yet.
I agree, Freedom From Religion Foundation, American's United for the Separation of Church and State, American Atheists, and The Clergy Project, and The Thinking Atheist!
Reminds me of a sign at one of the Women's Marches following 45*'s inauguration: "So bad even introverts are here".
There are numerous non-theistic organizations. In fact, that may be part of the problem.
I belong to the A H A -- American Humanist Association https://americanhumanist.org/ . I also belong to a not-exactly-non-theist group, Americans United for the Separation of Church and State https://www.au.org/.
Both work to protect the rights of non-theists.
Other wider-based groups like the ACLU protect the rights of everybody.
I guess at this time the best response would be for these various groups to work together. Which they often do.