In Fantastic Beasts and Where to Find Them movie, everyone calls Picquery "Madam President".
In Britain, there's Ministry of Magic (not Magical Parliament) and the head is called the Minister for Magic (not Prime Minister) who reports to the muggle Prime Minister. It gives me the feeling that the Ministry of Magic comes under the muggle government (only it's hidden).
As wizards already follow lots of muggle things like political boundaries of nations, names of nations/cities etc and they use muggle resources like roads, it looks good to give respect to muggle systems (as wizards can also be called citizens of a nation as they are humans), so even International Confederation of Wizards can enforce it (I am speculating the last part).
Was Picquery president of the Magical Congress of the United States only? Or, was she the
muggle no-maj (or, say universal) president of the United States?
Only canonical answers with proper citations, please.