What need is there for the English language to include both "affect" and "effect" [closed]

Is there ever a case where there is a sentence that would be ambiguous if the wrong word was used?

Yes.

Both words can be verbs*: "I want to affect/effect change."

Both words can be nouns*: "The affect/effect is pronounced."

is [there] a need to have separate words at all?

Probably not. English is full of homonyms and in some cases multiple meanings are grammatical.

I addressed the letter -> Did I put an address on it, or did I give attention to its contents?

The bat flew out of his hands -> A baseball bat, or an animal?

A huge crane fell into the water -> The bird, or the machine?

If we're able to deal with these ambiguities, we could probably live with a single spelling for affect/effect.

* The verbal form of effect is less common than the nominal, and the nominal form of affect is even less common, but they do, or did, exist.