Up through the 2010s, the internet was American military technology, ARPANET (1969, at the U.S. Department of Defense’s Advanced Research Projects...)
By the way, the Internet we usually use is only the publicly opened portion of the U.S. military’s lines, and above that there are three tiers of clearance: NIPR NET (UNCLASSIFIED), further above that the stand-alone (not connected to the Internet) SIPR NET (SECRET) servers, and further above that JWICS (TOP SECRET). (In the U.S. military, NIPR NET is color-coded green, SIPR NET red, and JWICS orange.) Also, Japan’s Internet, in an emergency, can be cut off and controlled under the management of the Ministry of Internal Affairs and Communications or the Ministry of Defense. (It is the same as closing the main valve of city gas or water.) Furthermore, it is possible to issue J-Alert (the nationwide instantaneous warning system) to each smartphone and terrestrial digital TV, etc.
This case is part of the Mandela Effect case database based on "The Window of Opportunity: A Guidepost to the Mandela Effect — The Ultra-Secret X-Files" by Aoyama Takuto.