Actually, churches in the U.S. are allowed to “advocate” on issues, and (to a more limited extent) on legislation related to those issues, according to the 50l(c)(3) regs. What they’re not allowed to do, by law, is endorse or oppose specific candidates or parties. Except, of course, in accordance with the BCFDCRGL (Black Church Freedom Democratic Civil Rights Gigundomundo Loophole.)
Having said that, I am so glad that the Catholic Church is not, and never has been, a member either of the NCC or the WCC.