Could the US really shut down the entire Internet by disabling its root DNS servers?. The answer is "No".

At the beginning of the World Wide Web, all Domain Name System (DNS) root servers were located on the US mainland. In the meantime there are also DNS servers outside the USA, so deactivating all American DNS servers would certainly slow down the performance of the WWW in the USA and in other areas. However, that would not be a worldwide shutdown yet. In addition, the DNS is primarily used to operate the World Wide Web, which is just a service on the Internet.