Protester shot in chest by live police round during Hong Kong protests

> Imagine if the US suddenly had a dictator

This is why we have the second amendment. And the constitution as the thing to which office-holders swear allegiance to rather than to "the party" or "the president".

If HK'ers had a similar right to carry guns, do you honestly believe that they would be any better off right now?

You really can't protect yourself from a government in a stable State, because the State needs a monopoly on violence to exist. Even in America, the argument from 2nd amendment advocates, that guns help protect American citizens from their government is absolutely ludicrous.

There is no realistic way for Americans to stand up to the entire US State with violence. Not without some very wide spread belief in the failure of the state, believe that would probably be easier to get with non-violent protest (and it still wouldn't be easy).

Read up on the civil rights movement, specifically Robert F. Williams. You have a situation where blacks stood up to their local governments that refused to convict whites for lynching blacks, local governments that refused to protect blacks from white violence, where police actually sought to disarm blacks in the face of white lynch mobs with little to no federal oversight, and all the peaceful protests in the south, the diner sit ins, and the freedom riders were backed by armed black men and the threat of reciprocal violence. I think that counts as a successful instance of Americans standing up to not only their hostile government but their adversarial fellow Americans as well.

And what if violence had broken out? How do you think that would play out?

Some counter examples are the Earth Liberation Front (ELF) or possibly even the Kent State Shootings (although there it was the State causing violence).

No matter where the violence comes from, the message tends to get lost from the reaction to the violence. Sure, even Gandhi talked about needing the capacity for violence for non-violence to work, but the moment things break down; the message may still get across or it may be totally drown out.