No, but "the" typically is, so the US is written The United States of America.
Yes it should always be capitalized.
The word citizen does not need to be capitalized.
It depends on the context. If they preced the name of a continent they do.
Yes. US Government is capitalized.
Yes. It is a proper noun.
US with both letters capitalized means "United States". The word us with neither letter capitalized means me and at least one other person.I live in the US.I went to the store to get us some groceries.
It should only be capitalized if you are referring to a specific constitution. For example, the U.S. Constitution.
No it shouldn't be capitalized.
To make a short answer short: No.
To make a short answer short: No.
Nope.
No