Both are grammatically correct. However, both are poorly worded.
A common sentence structure is "subject + verb + (direct object)". The reader / listener naturally wants to know (who) + (did what) + (to something) in that order. Both of your sentences say first (what happened) "assassination", then we wait to hear (who did it) "US", then lastly (who was ...
Either answer is true.
"Either" singles two things out, "both" groups them together. So when using "either", use the singular. A common expression is “either one”.
I have 98 Dollars.
More than one dollar means plural. Although there are some other world currencies which do not have a plural – “Yen” for example.
I have a 100 dollar note.
1) it is an example of informal usage;
2) formal usage.
3) wrong syntax.
There is a mistake in the grammatical syntax in the third variant, because it is obviously indefinite semantically. Semantic uncertainty of some kind is a feature of any informal usage. If the context and pragmatics are precisely defined in some communication and understood by the ...
It is optional to include or exclude a parallel structure in a comparison
He is closer to than my brother is close to me
may be shortened to
He is closer to me than my brother is
which may in turn be shortened to
He is closer to me than my brother.
Notice that, the wordiest version, the comparative clause is identical except for the degree of the ...
These all depend on the context of course, but I would consider five of the six uses completely standard. I don't think the use of "I feel" or "I'm (I am)" makes any meaningful difference.
The only one I wouldn't consider standard, though in a rather narrow set of circumstances not necessarily incorrect, would be the use of I'm cold = I have a low libido.
All of the sentences are grammatically correct: the first two mean what you intended, though I prefer the first version. The third doesn't make sense. To understand why, let's turn those three sentences around:
He will read Tom Sawyer and Robinson Crusoe in addition to the books I will read.
He will read Tom Sawyer and Robinson Crusoe as an extra to ...