Every country has their own laws governing handguns. Your license is for the US, under US (or state-specific) laws.
Firstly, you'd have trouble at the border, as you generally need permission or a license to carry a gun on-board a plane, boat, train, or bus, or across international borders.
Secondly, you would need a license under the laws of the country you're visiting to carry the gun, concealed or otherwise. These laws often differ depending on the size or capability of the weapon as well.
I'm sorry, just because you're a US Citizen doesn't mean you get to overrule the laws of other countries. ;) (no offense intended, just answering your original question)