What you're seeing is the fact that /j/ (English Y as in <you>) is a semivowel, which is paired with /i/ (English long-E as in <feet>). This means that the sounds are almost exactly the same -- the consonant version tends to be a bit more restricted.

https://en.wikipedia.org/wiki/Semivowel

EDIT: Also, the Spanish <ll> as /ʒ/ (S in English treasure) is not nearly as extent in South America as you might think. It's still mostly limited to Argentina and Uruguay:

https://en.wikipedia.org/wiki/Ye%C3%ADsmo#She%C3%ADsmo

EDIT EDIT: I misread the symbols a bit, and in other areas of South and Central America it's /ʝ/ instead of /ʒ/, which is not a very big difference at all. (Palatal vs postalveolar... Basically neighbors.)

> Also, the Spanish <ll> as /ʒ/ (S in English treasure) is not nearly as extent in South America as you might think. It's still mostly limited to Argentina and Uruguay:

In Puerto Rican Spanish (at least, my grandmother's family's accent), the <ll> is more of a /dʒj/ sort of thing. "llama" comes out to "djyamma", with the "dj" softened significantly. Not sure how to express that more precisely in IPA, though.

Maybe /ʝ/? That's the palatal version of /ʒ/, which explains your desire to add a /j/ in there.

The Wikipedia I linked is about the merging of <ll> and <y> to /ʝ/ if you want to read more. Interestingly, I don't hear this a lot in the northern Mexican Spanish I hear, even though all of Central America is marked as merged.

I didn't read it correctly the first time, and I was wrong to call it out in the first place. The difference between /ʝ/ and /ʒ/ is not so big for me to have said anything.

That was precisely what I was trying to allude to :) ‘ll’ is a soft ‘dj’ in Columbia also.

I find it fascinating how Greek ф became th in English and then was again reinvented as F. But English still pronounce all of the Greek ф’s as th.

I'm unsure what you mean by this... English <th> is inherited from Proto-Germanic, not Greek.

Also, did you mean Greek θ (theta)? θ started as aspirated /tʰ/, and it's a pretty common sound change for aspiration to become a fricative, in this case /θ/. φ also made a similar journey from /pʰ/ to /ɸ/ to /f/.

Phi is, I believe, pronounced as a voiceless bilabial fricative, which does not exist in English. Instead, we have the voiceless labiodental fricative /f/. If I remember my phonology correctly, Japanese uses the bilabial sound but in romanized text it's spelled with an f, which causes English speakers to use the labiodental sound.

Not sure why phi would be mapped to the voiceless interdental fricative ("th") though. I thought that came from theta. But I have not studied Greek, so I really don't know haha.

Modern Greek uses /f/ also. It was only /ɸ/ for a brief transition period. Spanish, however, uses the voiced version /β/ as an alternation for /b/, hence <Cuba> /kuβa/. (This is sometimes described as a mumble, since it's not a very common sound in Indo-European languages and people don't know how to interpret it.)

https://en.wikipedia.org/wiki/Koine_Greek_phonology

(Click through the "stop consonant" sections.)

FWIW, some (most? all? the one's I've heard, at any rate) Spanish dialects pronounce the letter 'f' as a voiceless bilabial fricative (I almost wrote 'phricative'). E.g. fotografia (sorry about the missing accent).

The letters 'b' and the 'v' are pronounced in Spanish as voiced bilabial fricatives after a vowel, and as stops after a nasal consonant (which in that position will be pronounced as [m]), and generally in utterance-initial position.