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I just got genki 2 and I don't understand what it means about なら. I heard it meant "if" from Tae Kim but it says

A statement of the form "noun A なら predicate X" says that the predicate X applies only to A and is not more generally valid. The main ideas of a なら sentence, in other words, are contrast (as in Situation 1) and limitation (as in Situation 2)

I have no idea what that's supposed to mean. It makes me feel like I don't speak english.

Situation 1 - Q: ブラジルに行ったことがありますか。Have you ever been to Brazil? A: チリなら行ったことがありますが、ブラジルは行ったことがありません。

So I guess thats supposed to be the one where it contrasts. I understand the second situation because it is just "if" but I don't understand the point of it in this one.

Is it supposed to emphasise that he's only been to Chile and not Brazil? Does it make that much of a difference if the なら isn't there?

I am afraid my answer will be a bit clumsy.

Situation 1 - Q: ブラジルに行ったことがありますか。Have you ever been to Brazil? A: チリなら行ったことがありますが、ブラジルは行ったことがありません。

Yes, this conversation could make if ~ sentence.

Q Have you ever been to Brazil? A : If it is Chile, Yes. but I have never been to Brazil.

I think what you are missing or seem to be confused at is the existence of the conjunctive particle, が，whose function reverses or changes the former statement.

So, here, with the conditional type of the auxiliary だ ( = なら ) and together with the conjunctive particle が、the sentence is making If **** Chile, but not been to Brazil. ( As mentioned above. )

And

Is it supposed to emphasise that he's only been to Chile and not Brazil?

Yes, it is.

And

Does it make that much of a difference if the なら isn't there?

You can replace なら with the combination of particles such as には、or auxiliaries combination such as であれば。 For instance,

チリには行ったことがありますが、ブラジルは行ったことがありません。( same meaning )
( Here the conjunctive particle が strongly affects the sentence. )

チリであれば行ったことがありますが、ブラジルは行ったことがありません。
　( Also here the conjunctive particle が strongly is affecting. )

Please give me a feedback should you not understand mine.

Thank you.

Without なら in that sentence, literally it still means "I have been to Chile, but not Brazil." But, the other party will be confused and think to himself, "I'm not asking about Chile, I'm asking about Brazil".

If you add なら, it adds the nuance or context that Chile is somehow related to Brazil in some way. Maybe because the culture or language is similar?

It also means, if you asked me about Chile, then yes I have been there. But, I've never been to Brazil.

Sorry, if my explanation is not based on grammatical correctness, but that's the function of なら in that sentence.

なら is the informal, conversational contraction of ならば. And that is simply the conditional form of the verb/copula だ. Much like 食べれば is to 食べる. Well, that is a simplification because it's a connecting word that has a life of its own. Considering the relationship to だ, even if it is only historic, is helpful.

Xだ。 → It is X.

Xなら(ば)、Y。 → if it is X, Y.

That speaker is conveying something like "If it were Chile (you had asked me about), then yes, but Brazil, no."

なら applies no nominalized clauses as well.

Xのだ。→ It is the case that X.

Xのなら、Y。 → If it is the case that X, Y.

The の usually disappears:

愛してるなら、行かないで。If (it is really the case that) you love me, don't go.

Speaking of だ and conditionals; there is a ~たら form of だ also, which is simply だったら, following the usual pattern of the past tense + ら. So there arises a similar question between choosing なら(ば) and だったら as between the えば and たら of any verb. Sometimes they can be interchanged. In this case, that person could have answered チリだったら行ったことがありますが、ブラジルは行ったことがありません。