Does the core Moneris payment processor work?
Our general strategy with payment processors is to get most of them out of core and into extensions, where they can be better maintained, so no, this is not going back into core. In fact, it's because Moneris didn't ever respond to the license questions about their mpgClasses.php file that it started falling out of core ...

I'd be happy to work with you to get the US code working. Contact me via the form:

http://blackflysolutions.ca/contact

with details about your needs and I can update my extension to support US$.

Alternatively - if your organization is a non-profit, I'd also recommend you compare iATS Payments services, they tend to be better (less expensive, more features, better service).