11th amendment puzzle.

[Dumander]

Hi folks.
"The judicial power of the United States shall not be construed to extend to any suit in law or equity, commenced or prosecuted against one of the United States by Citizens of another State, or by Citizens or Subjects of any Foreign State."

For me to understand it properly so I can explain it to others, I need to know details cause I was told by someone that it was meant only for disallowing Citizens to sue one of the United States........
Is it the comma after "equity," which separates the sentence telling us that the courts have no business at all?
I have a feeling that the comma didn't have to be there if the 11th was meant to be just for what it says about the "the United States not to be sued by Citizen......."

Also "one of the United States", does it mean that we have more than 1 United States (US listed as federal corporation) like US and USA or are they just referring to any state in this union?

The 11th is for me a kind of issue so please help me someone to clarify it. Thanks to all.