Many military commanders will tell you that it’s wise to cut the enemy’s lines of communication.
However, the US is concerned that Russia may take this advice one step too far. The New York Times understands that Russia is positioning submarines and spy ships near hard-to-reach segments of undersea data cables, hinting that it might sever internet connections in the event of a conflict.
As you might gather, that would create serious problems for the world as a whole, not just Russia’s enemies. Depending on the line, a cut could disrupt internet access (and thus economies) in countries that wouldn’t even be involved in the fight.