People normally say "in the US" or "in the USA".
No. But it would be correct to say. She joined us on April 10
If it is more than twoNo. We is a subject pronoun so doesn't go in the object position in a sentence. Us is the object pronoun form of we.So - "It is us" - is correct
Yes."you are with us people"AND"we are people"so..."we people"NOT"us people"
It would be more correct to say, someone who.
It is correct to say them both, but it matters on what you want to say.
It is correct to say "...serves more than 6000..."
Eyeing us is correct: for example, "They were eyeing us with suspicion."Note that for a similar-sounding verb, spying, it is correct to say spying on us.
No, because "let's" means "let us", and it does not make sense to say "let us join us." It would be correct to say, "Come on, let's join them." It would also be correct, if you are speaking to someone outside your group, to say, "Come on, join us."
Five is plural (more than one). Therefore, the correct sentence, grammatically speaking, would be "there are five of us".
It would be better to say: She gave approval for us to hold it'
"Both them and us were excited" is not correct usage. Look at how the pronouns would be used separately, then combine them in one, correct sentence. You would say "They were excited" not "Them were excited." Similarly, you would say "We were excited," not "Us were excited." The correct combination would be: "We and they were excited."
The more correct way to say this would be "It is humbling to be here". You can, as an alternative, say "I am humbled to be here."