Problem description: All world instead USA work in mm. But LO have strong lock to inches, for example, in such places as Business card creation. Basically LO have no any settings for switch everything to "system C" or metric. This is error.
Suggestion here is create switcher between USA and other world system. Paper sizes defaults can be switches in the same mechanism (menu). World use USA's paper types only when hardly depends from USA, on all other times it's standard metric A* sizes.
Let's make switcher.
Operating System: Windows 7
LO currently has a millimeter and centimeter setting. For example, right click on the ruler in Writer and click your desired setting.