A HEMP (High-altitude EMP) device is well within their capabilities (you only need a small pure fission A-Bomb), can be deployed clandestinely and with plausible deniability (wasn't us, it must have been that crazy Kim who done it), will yield very high return for the investment, and can cripple the US energy infrastucture for
years. If you think the "unrest" from the BLM riots are a problem, you ain't seen nothin' compared to the fallout from wide scale blackouts!
All they have to do is launch a satellite into a geosynchronous orbit (low earth orbit is not high enough for a HEMP) which then releases the device ("oops a meteoroid broke off one of our solar panels"
) which falls into a decaying orbit. It will be far far away from the satellite when it detonates. And it will be indistinguishable from space junk on radar.
Will they do it? They have to know that their own satellites will be damaged, so it's no small decision to make. And if they still have hopes of continuing to tap into the US consumer market for their goods, that will be severely hampered by an economic crash. Are they crazy enough to do it? Hell yeah!