From my perspective, based mainly on Czech jokes about these nations.
French:
Jean /
JeannetteSpanish:
Juan /
JuanitaItalian:
Giovanni /
DonatellaEnglish:
John /
MaryGerman:
Hans /
Hilda (
Hildegard)
Russian:
Ivan /
NatashaUkrainian:
Volodya /
OksanaSlovak:
Jožo /
MáriaSouthern Slavic:
Zoran /
ZorkaRoma people: Dežo /
ArankaJewish people:
Isaac /
Sarah (or
Rachel)