Only thing I can find on international observers is about North Carolina excluding them [0], and this:

CBS News: Trump's attempt to stop vote counting "a gross abuse of office," international observers say. https://www.cbsnews.com/news/trumps-international-observers-...

[0] Raleigh News & Observer: North Carolina says no to international observers at election polling sites. https://www.newsobserver.com/news/politics-government/electi...