Also, distances were vastly bigger (maybe that's included in positioning?). England had to ferry troops and material over the Atlantic at a time when a ship voyage was long and could very well end in disaster. China could move troops over in a matter of days without any real risk.

America also had the financial and military support of France.

You act like the American revolution is the only instance of this. The French Revolution is another example of people fighting for change.

The French Revolution was largely fought internally. Hong Kong’s situation is more like occupation than civil strife.