>>Die Bill of Rights sind die ersten zehn Zusatzartikel
You can have a plural verb here in German, but not in English. As someone explained in #7, in German the verb can agree with the predicate, or rather, the subject can follow a linking verb. Here, 'sind' agrees with 'die ersten zehn Zusatzartikel.'
But 'die Bill of Rights' looks like a mistake to me, because 'Bill of Rights' is singular. (Singular. Singular. One bill. Repeat that to yourself, please. (-; ) And as far as I know, the possible translations for 'bill' are all neuter: das Gesetz, das Dokument.
In English, the subject is always the noun that comes before the linking verb. So the rest of the sentence is not important. If the first noun is 'Bill of Rights,' then the verb after it must be singular:
The Bill of Rights is / consists of the first ten amendments to the Constitution.
The part about the division of powers (in the US, we call it the balance of powers) and Montesquieu is really your job, no? (-: