If a case goes to trial, there will be a jury pool of potential jurors, and each lawyer will have a chance to ask them questions. This is called voir dire.
After this question period, the lawyers are allowed to kick off possible jurors “for cause” (meaning they are obviously unsuited for service - maybe they can’t understand what’s going on, or have a medical situation or an unavoidable conflict).
Next, each lawyer can eliminate people “just because”. These are called peremptory challenges, and you only get so many. Important to this OP, however, you can’t use these challenges to eliminate a protected class of people.
At the conclusion of this process, you winnow down the jury pool into your selection of jurors.
If, at this point, one of the lawyers feels like there is a tainted jury pool, they can challenge it. This is called a Batson challenge (based on the name of a Supreme Court case), and traditionally is applied to race (I.e. you end up with an all white jury after all of the black candidates were eliminated).
So, here, a lawyer may say “wait a minute. Everybody is the same religion. I’m objecting to this jury.”
But if the other opposing attorney has reasons for why they kicked off certain people that are not related to their characteristics (in the OP’s case, religion), then the judge will still likely accept the jury. A jury of people all of a certain religion - who have sworn to the court and the lawyers that they can set aside their faith to the extent necessary to be impartial and consider the evidence presented - aren’t inherently unqualified to serve.
This could, and likely would, end up an appellate issue.
(I should emphasize that religion is not as well defined, I believe, as a protected class for purposes of a Batson challenge as compared to race or sex. If somebody is ultra religious, to the point that they said they’d pray about the verdict instead of considering the evidence, I’m sure it’d be ok to eliminate them. But just being devout would not be an ok reason to kick somebody off, I’m sure)