The Cambridge Grammar of the English Language (Pages 427-28) has this:
Universal personal pronouns of the type us all
[6] i a. They’ve invited us all. b. It’s an insult to us both.
ii a. She likes you all. b. I’m counting on you both to help.
iii a. This applies to them all. b. I expect them both to take part.
Here we take all and both to be incorporated into a compound pronoun. These forms are to be distinguished from the sequences found in the much more general construction seen in:
[7] i a. We all/both enjoyed it. b. We had all/both enjoyed it.
ii a. You each qualify for a prize. b. You will each qualify for a prize.
iii a. They all five of them complained. b. They are all five of them complaining.
In this construction the underlined expressions are quantificational adjuncts functioning in clause structure. This is evident from the fact that when the verb is an auxiliary they preferentially follow rather than precede it, as in the [b] examples. Note also the possibility of inserting an adjunct after the pronoun and before the quantificational adjunct in [a]: We certainly all/both enjoyed it. No such insertions are permitted in [6]: *She likes you certainly all. A further important difference is that in the adjunct construction the pronoun can be replaced by NPs with common noun heads: The girls all/both enjoyed it. Again, such replacements are quite impossible in [6]: *They’ve invited the girls all.
The adjuncts in [7] have the form of fused-head NPs. As the examples show, the pattern extends beyond all and both, covering each and partitives that are excluded from [6]: *It’s an insult to us each, *This applies to them all five of them. The combinations in [6] are thus not predictable by any general rule, and are best regarded as compound forms; they are limited to the six accusative forms cited.
[6] describes six compound pronouns us all, us both, you all, you both, them all, and them both. And [7] describes fused-head NPs containing all, both, or each. Per CGEL, these NPs are quantificational adjuncts functioning in clause structure and are to be distinguished from compound pronouns.
CGEL says further that compound pronouns cannot have each as in us each, you each, them each. Hence, the ungrammatical *It’s an insult to us each. But why can't each belong in [7] in It’s an insult to us each?
Here are some examples where us each, you each, or them each is used:
The point is not really whether $200,000 is reasonable; it is that the very notion of attaching a dollar figure to an experience as momentous as parenthood is a sign of how much my mind-set has been warped by this system that leaves us each so very much on our own, able to avail ourselves of only what we can pay for. <The New York Times, 2019>
All I need you to do is carve out two nights a week until the wedding to help. I’ll send you each a supplies list, and to make sure the cost distribution is fair, please send me a confidential email stating how much you earn — tax forms or pay stubs are fine. <The New York Times, 2017>
It’s mid-May, it’s beautiful out, and your students are restless. One solution: Hand them The New York Times.
Next, ask them each to pick one article — any article, for any reason — read it, and tell us in the comments here why they chose it. <The New York Times, 2018>
If these are all fine, why isn't It’s an insult to us each?
