At a minimum, we can keep the issue at the forefront of everybody's mind so that the US government continues to monitor the situation in Cambodia and does not turn a blind eye.
The closure of the notorious Svay Pak (aka km11) as depicted in the video link came as a result of international pressure.
The underage sex trade has merely gone underground, not disappeared.
We can only influence policies indirectly.
The Cambodian government has a lot of contempt for overseas Khmers who criticize their policies or them.
The Cambodian government will not listen to us but will at least make an effort to clamp down on the most outrageous acts of pedophilia and other things, as a result of pressure from various governments.
How do we keep the issue at the forefront of people's minds?
(1) by doing what we are doing right now: having meaningful discussions about the issue.
(2) by not being ashamed to raise the issue in public forums, at college or wherever, i.e. by not worrying that we are giving Cambodia a bad name, by publicizing a violation of human rights that brings shame to Cambodia and all of us. By keeping quiet for fear of bringing shame to Cambodia and Khmers, we are not helping. It is tantamount to protecting incestuous behavior or all kinds of abuse (e.g.. domestic violence) for fear of bringing shame to the family.
The more people know the truth about Cambodia, i.e. how bad Cambodia is, the better.
The leaders may start thinking twice about going too far and more and more pedophiles and sex tourists may start thinking twice about coming to Cambodia.
The relevant international authorities may think twice about their "softly, softly" approach in Cambodia for fear of upsetting the Cambodian government.