How can I circumvent regional restrictions in Google's Play Store?
Try the Market Enabler app (download the APK and side-load it.)  It allows you to spoof your region, so that the Market thinks you're in the US.

As an alternative, you may want to see if this app is available via other distribution methods, such as from other reputable markets (e.g. Amazon Appstore, SlideMe.org, GetJar.com, etc.)  Also reaching out to the developer can sometimes help.