Hi there,
I'm afraid I'm not a US native, but I do entertain America audiences, through several accounts. English is my first language and I'm familiar with US (and UK) slang, so I experience no difficulty whatsoever, in getting my thoughts and ideas across.
I manage a client's Twitter account and interact with followers on their behalf. Both the client and their audience are US-based. In addition, my own Twitter account has a lot of followers from other countries, including UK (chiefly), US, Australia and China. Lastly, my Facebook friends are largely American, and find no problem understanding me - although they do think I have an accent when it comes to voice recordings (which won't be a problem here).
Please message me with more details. What will the articles be about, and what will their average length be? I'll let you know my fee accordingly, as I think per-article payment is more convenient and simple than hourly payment.
Thanks,
Priya