The common usage of measures you will see in most any EU country is Si, it is required by the EU for membership to standardize on Si. However the French, like many other nations have their own customary units. As it relates to this post, and in context to Vietnam- France was still using their customary units along side the metric system when they were defeated in Vietnam. Units like the Poncelet, and later their own unit with the same standard as metric but with their own naming conventions. So if we discuss countries which are not on the metric system at the time they were defeated in Vietnam...
This is why y'all lost the war.