You turned it into a major repair. Yes, it is there responsibility to fix it and re-hang it, but unless it is an immediate hazard to yourself or others in the area then you had no right to cut it.
Cutting off internet access in that way to a number of entities because you were mad at comcast for making you drive under boards is irresponsible, petty, and juvenile. You were wrong.
If a water main junction was leaking water onto your property causing a non-trivial otherwise inconvenient problem for you, would you be justified in grabbing a wrench and shutting the whole thing off?
For anyone who doesn't want to be a that guy -- in such situations try calling 211 which is the national line to get someone to help you to connect to the appropriate agency, which would probably be the FCC Public Safety Support Center
Or, escalate the call in comcast -- ask to be transferred to the local division network operations or whatever but don't fucking cut the trunk line.