A very thought-provoking video, if you stop and think about it.
But few people realize that in the past, the Posse Comitatus Act prevented the use of the Army or the Air Force for domestic policing except in dire situations that first require a local (by state) declaration of state of emergency as well as a supporting declaration of martial law. Without the latter, a governor may call up National Guard units (independently of their parent unit) to support the state police (or equivalent) in maintaining peace and order. Suspension of the Posse Comitatus Act requires a specific request to and approval by US Congress before any troops can be called up for domestic service. Not covered by PCA is the Coast Guard. During peacetime, USCG falls under the Department of Homeland Security and not the Department of Defense, unless the parent US Navy units are activated with the approval of Congress.
The Insurrection Act, however, allows the Department of Homeland Security to sequester and attach to itself any such reserve or active military units (regardless of branch of service or status of parent unit), even absent a local (state-level) declaration of state of emergency (and therefore would supercede local government action or inaction), to deploy to locations statewide or nationwide and act in a police role to control "civil disobedience" and/or "civil unrest". DHS can do this without consulting Congress, or even without the consent of Congress, "by direction of the President".
The Insurrection Act has indeed been invoked most recently during the race riots in Los Angeles. US Army units were deployed to assist state and local police in controlling the "civil unrest". In a situation such as this, any individual who resists "proper authority" (meaning the police or the military if present) can and may be declared to be in active insurrection against the government of These United States. In other words, an Enemy of the State.
DHS, whose jurisdiction ends at our international borders, does not have or maintain prisons, and an Enemy of the State will not be sent to just any prison but a Federal Military Prison (such as Fort Leavenworth), which is operated not by the Department of Corrections, but by the US Army. So a person declared a "terrorist" will be remanded into military, not civilian, custody. This is normal, since our "declaration of war against terror" has not been repealed.
Now, all this may sound scary, but the bottom line is this: YOU as a person (and this means the corporeal "you", not any given individual by name) should have nothing to fear if you have not done anything wrong or that may be construed as being "wrong" in the sense of:
1. Supporting terrorism, known terrorists, or terrorist activities
2. Plotting with others (typically using the Interent) to plan or prepare plans to support #1
3. Discussing ways and means (which may be interpreted as "plotting") to conduct activities against the government or any branch thereof
4. Discuss ways and means to conduct activities that may be interpreted as encouraging the overthrow of the government
Jack the Plumber (can't use "Joe" anymore), Joe the Roofer, Mary the Grocer, none of them should have anything to fear from the government (except higher taxes and maybe more restrictive laws) unless they do something out of the ordinary that would call attention to their statements or activities.
Simply put, while the government now has the power to do all those things simply "By Direction of the President", unless something happens that is remarkably intense and traumatic to the country as a whole, there should be nothing to fear as far as the Army patrolling the streets of Anytown, USA. And if in case something like this does happen, I would hazard to guess that we would by and large be grateful for their presence to calm the location.