can you delete contact tracing app from iphone 12

There is no contact tracing app on your phone. They have to be downloaded from the App Store and that would require user input. The iPhone does NOT come with any contact tracing apps pre installed.

If you downloaded one on your own, yes you can delete it.

That’s is not an App. It is a setting that gives functionality to contract tracing apps. You do not have to enable it if you don’t want to use a contact tracing app. It does nothing by itself unless you turn it on to use with an app that you would have to download.