Well for this one I'm going to say that it is still a theory no matter how deep, but for this one i'm going to focus mainly on "Other gems on earth  " but i will try to continue it on a later date.

So from Ronaldo we know that gems are known in the government, or in a Illuminati way.

1) Protection: 

So if gems were to exist on earth, which is actually FACT because of all the creatures they battle on earth that were gems and all of the magical gem places like the island from "Island Adventure" . So now we have a layout that isn't theory but is fact. Actually their may have been more groups other than the crystal gems, so maybe they got their place on the bill because of protecting us. Maybe they were use in armies to fight and maybe that'show the gems were corrupted.

2) Government: 

Ok so if gems were to take leadership of being president they would have to be:

Smart

A Good Leader

To Protect Us... I guess...

And Able To Pass Laws And Give Speeches

all of these off 

With the crystal gems as an example we can check these all of these off so it could be possible.

Oh and since it is a diamond the first president could've been Diamond, but it'd be a shame since 4 years is like nothing for gems. 

3) A secret club

This one would most likely be the answer because the crystal gems are a secret club anyways, but it makes you laugh when you realize that they made it resemble the Illuminati by turning it upside down to resemble a pyramid. (This would make the best fanfic!), but it also brings the question: who is the club and where are they?

{Well that's all I can write for now, PS: It's like 8:00 AM and I need to have some b-fast!} So bye!