Revit mEp is very American because it is hard-wired to do its calculations based on the AWG based wire sizes that are defined in the templates Autodesk provides to us. When you need to reference metric sizes/standards instead there is no place to change this bias and if you attempt to change wire sizes to metric equivalent (CSA or Sq. mm) values you'll find calculations, like Voltage Drop, either cease to work or you get strange results.
Working through this issue with a client recently they decided (or at least hoped) it would be acceptable to provide a chart that allowed the reader to cross reference the AWG size against the locally relevant size. This firm is based here in the USA but working on a project outside the USA. Perhaps in that context this could be forgiven by the client. I don't know how well that approach will work for firms that are working at home, outside the USA.
Fwiw, Autodesk IS aware of this bias. Providing more flexibility is among the many things they have to find time to include in future releases.