Should I set a target in G webmaster tools?

I have an ecommerce site which is doing well for its target keyword. It is on page 1 for the keyword pretty much across the globe. My major market is the united states, however I can ship worldwide, but orders are unlikely due to high shipping costs. I am currently ranked #8 on google from the US, and am trying to get higher.

Should I set the target for webmaster tools to US? WIll this help me get higher in the google rankings? or will it just knock me out of the international rankings?