You don't outright lose years of experience writing C and C++ just because you learned Ada. You're not going to leave a decade of C experience off your resume just because it wasn't the primary language in your last position. Ada isn't for frontend web development where new "technology" gets chewed up and spat out every year or two. It shines in firmware. There's plenty of vendors that haven't moved past C99.
Chalking up a hypothetical appreciable Ada marketshare in automotive as "niche stuff only used in the auto industry" doesn't make sense in that it sees plenty of use in aerospace, defense, and medical. The point of me bringing up AUTOSAR is that Ada is nowhere close to the pigeonhole scenario that AUTOSAR is.
In the world where you only have Ada experience, and you're not a bad programmer, but HR departments are giving you grief, just lie on your resume. Fuck em. We both know that it's not a major adjustment, so brush up on details before you're interviewed and if they asked what you used C/C++ just say you're not at liberty to speak about it. Nobody is going to hit you with anything along the lines of whether or not it's true that monads are just monoids in the category of endofunctors.