Metric. by the way, is actually American. It was Ben Franklin who came up with the system
As with most of the things that are claimed without citing sources, this is dubious. Why would Benjamin Franklin name an International System "SI" as in the french: "Systeme International" ? Why not have a look in an encyclopedia and see what they say about that ?
It is masked but always present. I don't know who built to it. It came before the first kernel.