All those are just hunks of metal if the clerks and secretaries don't process the paperwork that keeps them supplied with fuel and spare parts. And the clerks and secretaries are subject to persuasion to quit from their fellow citizens.
Targetting the secrataries wouldn’t do much to undermine the image of you being terrorists, which would increase support for the government, also, the government could buy weapons and supplies from foreign governments, who would be all to willing to support your government, because watching the US collapse into civil war and anarchy isn’t exactly in anyone else’s interest, and they would want to see any meaningful revolt crushed as quickly as possible so that business could go back to normal...
Just as an example, the IRA in Northern Ireland often murdered any Catholic they saw as being a ‘collaborator’ with the government, not just police officers, but canteen workers at police stations, and even census officials. That lost a lot of support in the Nationalist/Republican community because of the violence and fear in which they held their community....