Notices

Yes you could look at a betamax provider like http://www.voipbuster.com/en/sms-rates.html
Webtexter works fine with that one.

But as you can see in the above rates USA is almost the most expensive one to send sms to.. But i have no idea what you normally pay for sms in the states?
You can look if other betamax providers have better rates for you:
http://backsla.sh/betamax (this is just phone rates, there the usa is very cheap, even mobile phone calls are mostly 0, thats really cheap compared to my countries to mobile phone calls, which are really ridiculous for the most part)