To start with, an effective attention getting introduction might include describing the experience of one victim of child trafficking, especially an ethnic minority child, not letting on until the end of the story that it takes place in the United States. There are many such stories to choose from on the internet, but you might try either the United Nations website or the Center for Missing and Exploited Children as reliable sources of information.
For a thesis, and since your audience will universally agree that child trafficking is both morally reprehensible and a serious social problem, you might argue from the angle that the United States/United Nations needs to take much more concerted and immediate action to combat trafficking, i.e. that it is not taken seriously enough in the US, and public awareness of how widespread the problem is remains very low. You can suggest that new funding be set aside for law enforcement and interdiction of traffickers and networks, and you can also call for a well-publicized information campaign with a national system/tip hotline where citizens can participate in ending the practice.