Or the US is preparing for conflict with China, so China must also. But actually it's probably a two way feedback loop between the two of them that the ignoramuses that run each country love because it makes their jobs exciting and, probably, profitable.

All powers are mutually antagonistic and it prudent to prepare to confront each other. As long as thoes efforts are equally matched and neither side is prepared thinks it can gain an advantage the peace is held as it held during the cold war.