If there were months of mass protests in the US, the national guard would be called in to stop them, with full military equipment. This is what happened in Ferguson, for instance, and the police there did shoot and kill at least one protester.
What happens domestically, we refer to as riots. What happens internationally, we refer to as protests. During the LA Riots, over 10,000 national guard troops were called in, and the police and Guardsmen killed at least ten people - either rioters, or protesters, depending on your perspective.
Many of the protests in Hong Kong have been anything but peaceful. They are throwing Molotov cocktails, destroying buildings, smashing and flipping cars, setting fires, breaking into the Legislative Council building, taking over the airport, physically attacking the police.
In Hong Kong, the protests began over an extradition bill which would have subjected Hong Kongers to Mainland China's opaque justice system. That's a pretty good cause for protest, but it doesn't strike me as significantly more noble than wanting the police in the US to stop shooting young black men, for instance.
Here's my weird position: I support the Hong Kong protesters and their goals, and even their methods. At the same time, I think it's weird that Western media consistently portrays the police in Hong Kong as aggressive. To my mind, they've been significantly _more restrained_ than the police in most Western countries would be.
If people are rioting, it's perfectly natural the police would take aggressive actions to stop that. No one gets to decide that it's okay to riot without repercussion.
At the same time, some of the fastest positive change that has happened in society came as a result of rioting. Only history gets to decide if it was justified.
No arrests, nobody got hurt. There is more than one way to operate.
https://www.npr.org/sections/thetwo-way/2016/07/19/486581466...
https://m.huffpost.com/us/entry/us_578cf018e4b0fa896c3f4a0a
https://www.kwch.com/content/news/National-Black-Lives-Matte...
https://www.businessinsider.com/black-lives-matter-protester...
Protesters in America need permission from the government. If we were to block roads like they are doing in Hong Kong it would spell certain disaster. More than a few places offer legal protection to people who run over protesters with their vehicle.