The US has a good number of non-nuclear submersibles for specialized missions such as SEAL team delivery, deep diving rescues, sensor & mine delivery.
But all the true submarines are nuclear, including SSNs, SSBNs & SSGNs.
There has been some interest in adapting German Type 212 non-nuclear AIP subs (super-quiet) for littoral combat roles, but so far, nothing specific has transpired in that direction, that I can find.
My Grandson is an engineer at Electric Boat.