I agree with you that the current model has nothing to do with the benefit to society. However, the current model is all about keeping economy running. USA is overall a technological powerhouse with no equal in the world, China comes as a second but it was built up with American companies investing giant amounts of capital about twenty years ago to produce stuff cheaper.
Right now there is a shift away from producing stuff in China, so American companies are unlikely to do a second round of investment into China to modernize those factories. More likely there will be domestic investment into robotics driven factories here which would put those out of date Chinese factories out of business unless China invests its own capital to bring them up to the new robotics / AI standards. Even then China cheap labor advantage will be gone...
Public debt by itself is not a problem it is leverage that let's you pump up your economy particularly when dollar is the reserve currency... The only problem is when rates are high the interest payments are becoming expensive, but here we have Fed to the rescue with their rate cutting program...