The private water utility company is a false equivocation. Government regulations view this as a natural resource and regulate it heavily. Privatization of natural resources often raises the specter or threat of cut-off as you suggest and is traditionally subject to government intervention.

I believe you are right - cutting communication channels of a sovereign state can be an act of war. But these are private channels. I don't think we are anywhere near classifying these platforms as public utilities, much less natural resources, at least in the United States.