which prohibits churches from endorsing and fundraising for political candidates

That's not accurate. The Johnson Amendment is not a ban on churches, it's a ban on 501(c)(3)'s. Also an organization can split its activities among different tax entities. For example the ACLU does this.

Legally, the ACLU consists of two separate but closely affiliated nonprofit organizations: the American Civil Liberties Union, a 501(c)(4) social welfare group, and the ACLU Foundation, a 501(c)(3) public charity. Both organizations engage in civil rights litigation, advocacy, and education, but only donations to the 501(c)(3) foundation are tax deductible, and only the 501(c)(4) group can engage in unlimited political lobbying. The two organizations share office space and employees.

The idea that are banned from politics is a canard. They just are banned -- along with other 501(c)(3)'s -- from using tax deductible donations for certain political activities. If they're willing to use non deductible donations and go through the paperwork of setting up a separate corporation, they can electioneer as much as anyone else can.