A GNU system built using a Linux kernel would then reasonably be called a GNU/Linux system, but that would not be the name the system. It would be a statement that it is a Linux system that meets the GNU specification.
The naming rights to a system historically go to whoever puts it together. So the complete system that Red Hat sells is the Red Hat Enterprise Linux system. That's its name, because Red Hat put it together so they get naming rights.
The complete system my past employer, Interactive Systems Corporation, sold that consisted of System V ported by us from the 3B2 sources to the 80386 was a UNIX system, but its name was 386/ix. We are the ones who put it together, so we got to pick the name, even though very significant components came from outside.
When describing the system named Red Hat Enterprise Linux by capabilities rather than be name, then it can be called a GNU/Linux system because it satisfies the functional requirements to be a GNU system.
For giving credit to those who provided the components you used to build your system, the traditional place to do this would be in the documentation and if you have a GUI in the "about" box of some major GUI component, such as whatever corresponds to Apple's Finder or Window's Explorer on your system.