To what extent can it be said that Shylock is a type of Jewish nation and Antonio a type of Christianity?

don't think either character represents a nation state be it Israel or say Christian America. They both represent certain stereotypes as seen in Elizabethan England. Shylock is a caricature of "Jewishnes". He is old, miserly and stubborn. Antonio is seen as much more fair. Both work under stereotypes though but through Shakespeare’s magic they are human beings with similar traits.