probably but it will only partially shut down the internet
these morons don't understand how resilient the tech is... every week for a few months i was walking past a data centre that had two diesel generators
i haven't seen the installations associated with teh undersea cables here in Madeira but i can assure you that there is 5 different ways that messages can pass from here and if any one of them fails within milliseconds they start sending them in another direction that works
the undersea cables are not vulnerable to the EMP.
the installations that repeat the signals on the islands and under the water are not vulnerable to EMP, most of the actual cable runs on the land are underground and they fan out like the bejesus and many of them have inactive failovers that have zero power in them and many of them are housed under mostly metal shielding and are often virtually faraday cages with earthing
it's just not possible to shut down the internet
they can shut down people's brains, but they can't shut down the internet, that's gonna be really really bad news for their objectives