Hi Sir,
We are Iton Corporation. We are leading SMS Aggregators based out of Dubai. We have ready APIs which you can call to send SMSes to around 185 countries in the world. This includes the 4 countries that you mentioned - USA, Canada, Australia, UK. You shall be charged as per the usage levels on per SMS basis to the appropriate country.
Please get in touch, I can associate my business and tech leads to help you with. Our Services are offered through cloud. We support both SMPP and API for easy integrations.
Regards
Savith