Please have a look at this assignment:
"Point out in how far the American Dream has become a nightmare."
It is taken from a German textbook for English learners at an advanced level ("The New Pathway Advanced"- Schöningh p.140):
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For me personally "in how far" sounds totally normal (I'm German). However, a British person told me that it sounds wrong to his ears and that it should be "how far".
So I was wondering whether "in how far" is American and "how far" rather British?
Or let me ask, is there a rule when to use "in how far" and when "how far"?
Best Answer
I understand in how far as synonymous to to what extent, as its structure is exactly the same as that of Dutch in hoeverre and German inwieweit (both, literally, 'in how far', meaning 'to what extent'). That's what I make out of it being a native Polish speaker who is familiar with those other two languages. No idea if it's idiomatic in any native variety of English (most Google results for in how far I've found seem to be texts written in English by German native speakers).