I don’t think one can expect even the slightest resistance from the police in a crisis, since their leadership is largely made up of the same people who elected these crooks to the White House.
I believe the circumstances surrounding the military’s current war against Iran - a war that violates both international law and U.S. law, during which they are committing the most serious war crimes - clearly indicate that no resistance is to be expected from them either. Furthermore, all generals critical of the regime have already been removed.
In Short: Both the police and the military are led predominantly by MAGA officials who would benefit from the establishment of a dictatorship. I therefore do not think they would offer resistance in a crisis - they could do so right now given the obvious crimes the regime commits on a daily basis, but they just do not.
I think it will simply turn out however the oligarchs who actually control the U.S. decide. If they want a dictatorship modeled on the Russian one, that’s exactly what will happen.