The US has over 10,000 military aircraft in service and thousands of spares sitting in storage. The US is quite arguably the only military that can casually absorb losses like these.
This specific aircraft is being phased out over the next several years. Assuming these still had some miles left on the airframe, they likely would have been put in cold storage a few years from now.
Do you have a source for the Growler being phased out? I was under the impression that they still have a long operating life ahead.