*Take over the media (simply not possible in America
due to the volume), initially to block
information
*Take over the Military (Too large and diverse
to accomplish in America.)
*Arrest/Detain all political opposition.
(there are simply too many local governments
in America for this to happen.)
#1 is entirely feasible. #2 is entirely possible as well - there are lots of revolving doors with defense contractors and the DoD... heck, just read through the Patraeus scandal [1]. This a 4-star General (Commander of CentCom), Director of CIA and was a likely presidential candidate - just read through the tawdry and incestuous relationships within the community, and wonder at how easy it'd be to simply bribe everyone with an offer they couldn't resist.
[1] https://en.wikipedia.org/wiki/Petraeus_scandal
I posit this can be planned indefinitely. Once the hammer drops, yes countdown time is hours, but... take a look at the 2000 election results and the weeks it took to finally stop the clock on vote counting.
[1]: https://en.wikipedia.org/wiki/Concentration_of_media_ownersh...
Fox isn't a major network? (Or did you mean "not carried on other major networks?)
As an example in the U.S., let's say that 3/4s of Republican governors, along with half of Republican Senators, and an absolute majority of the House, the vast majority of their individual financial backers, and a large number of generals decided that Trump lost due to voter fraud that occurred largely in states and cities with Democratic administrations. A group of them then read an open letter on Fox News about it, and the reading, while not carried on major networks, is broadcast on all channels by Comcast, Altice, and Cox Cable. As the letter is being read, a mass email goes out to the Trump email list to converge on the White House in DC and Clinton Foundation headquarters for a peaceful protest, named "Occupy the Crooked Election." As the thousands accumulate, the Governors that can announce that they're going to mobilize the state militias to do a recount, or rerun the election.
Is this impossible? How do you walk it back? Also, didn't we just have a massively blood soaked civil war 150 years ago?