I think perceived legitimacy, or a lack thereof, will outweigh the hatred the American managerial elite has for its citizens and its self-preservation instincts & plans if affairs degenerate to a shooting war. I don't doubt they would quite like to remain on top, and to go to any length to maintain their control, but unless they happen to have developed a robot army in complete secrecy under Cheyenne Mountain or something, it's not going to matter if they can't motivate the vast majority of the armed forces & police to continue doing their bidding and really start laying into the American people. Worst they can do is draw their own deaths out some more and take more people down with them while they're at it.
If brute force and a murderous contempt for your own citizens was all it took to maintain absolute control, the August Coup - spearheaded by agencies, generals and apparatchiks with open totalitarian control over the lives of their subjects, and whose disregard for human life must have at least matched (and more probably exceeded) that of the worst 3-letter agencies - should've preserved the Soviet Union, not killed it. There will always be bullies in uniform like that SJW Bronson whose video was posted up on this very page, as there were Soviet troops who were still willing to open fire on the enemies of the regime in the very last days of that regime.
But once the rubber hits the road, how many US soldiers will be able and willing to gun down crowds and/or militias - or even their own fellow soldiers and National Guardsmen who've defected to the opposition - in service to the government that just rendered 20 years of their blood, sweat and tears not only pointless, but turned it into an absolutely spectacular international embarrassment which will potentially dwarf even the Carter years, weeks before they are reminded of all of what it was supposed to be for in the first place? Will cops still bother to do as their chiefs and DAs and mayors say, and save Antifa from the consequences of their actions when it's not probably-glowie Proud Boys with non-lethal weapons beating them in a street skirmish but rather a mob of uncontrolled and armed vigilantes which are openly out for their blood?
And if they still are willing to do the establishment's dirty work, how many times can they be expected to do it until they get tired enough of serving a regime that increasingly blatantly doesn't care about them; doesn't know or care what it's doing past making the deplorables hurt; and has no goals beyond self-perpetuation and spiting the groups it despises (including the armed & police services themselves) that they stand down, desert or defect? At least when PLA tankers were running people over at Tiananmen in service to Deng Xiaoping, they could claim 'hey, at least that guy made life better for us' and it would be true compared to the horrors of the Mao years - what can America's managerial technocratic class say they've done for the thin green & blue lines recently? I think the answers to these questions is what will ultimately determine the longevity of the establishment in a hot civil war.
(Nukes, I think, we can safely take off the table - if anything using one on your own home soil, besides destroying the country you're trying to keep ruling, would kill your legitimacy and deprive you of your remaining supporters quicker than any August Coup lookalike would; not for nothing did the Soviets refuse to use theirs to preserve control of either the Warsaw Pact or their own Union)