Q:

"Us Americans" or "We Americans"?

If there is a group of individuals identified by a name, what's the right way for one of the group to refer to them all?
For example, if one of a group of 10 Americans wants to refer to the group, is it more correct to say "Us Americans" or "We Americans"?

A:

What are the Americans doing?
Apply the usual "we vs. us" test: Remove any nouns and adjectives between we/us and the verb, and test.

[We/Us] drink beer cold : We Americans drink beer cold.
The Aussies call [we/us] Seppos : The Aussies call us Americans Seppos.

The same test applies when referring to any group collectively:

[We/Us] recite poetry to appreciative audiences: We
  Vogons recite poetry to appreciative audiences.
The "Hitchhiker's Guide to the Galaxy" describes [we/us] in
  highly disparaging terms: The "Hitchhiker's Guide to the Galaxy"
  describes us Vogons in highly disparaging terms. (A lawsuit is pending. In triplicate.)

A:

To address the points that @FumbleFingers raises in his bounty:
Merriam-Webster Unabridged offers these observations in its definition of the pronominal us (albeit not without some nose-holding, and a few pokes at "grammarians"):

f — used by speakers on all educational levels and by many reputable writers though disapproved by some grammarians in the
  predicate after forms of be, in comparisons after than and as
  when the first term in the comparison is the subject of a verb, and in
  other positions where it is itself neither the subject of a verb nor
  the object of a verb or preposition:

the miraculous generation which is us [Arnold Bennett]
you are bigger and stronger than us women [K. A. Menninger]
us and our little problems

g (1) — used chiefly in substandard speech and formerly also by reputable writers as part of the compound subject of a verb or
  especially with an immediately following appositive noun as the
  subject of a verb which it does not immediately precede

our neighbors and us don't like that
us kids were always given a swallow [Walter Karig]

(2) chiefly dialectal — used as the subject of a verb from which it
  is not separated by other words

us lived in a two-story house [Ralph Ellison]

h — used like the adjective our with a gerund by speakers and writers on all educational levels though disapproved by some
  grammarians

she approved of us getting summer jobs

Likewise, M-W Unabridged defines these (ahem) non-standard usages of the pronominal we:

3a dialectal, chiefly England :  us — used emphatically as object of a verb or preposition

to poor we thine enmity's most capital [Shakespeare]
the likes of we

b chiefly substandard :  us — used in a compound object or in apposition with a following noun

he disturbed those in the dining room, those in the hall, and even we    who had retired upstairs
as to we men [Fanny Burney]

A:

I agree with the rule of thumb described elsewhere which recommends using "we Americans" or "us Americans" depending on whether the context calls for the subject or object pronoun. This is the standard practice, as corroborated by a corpus search.
For example, if you search for "we Americans" versus "us Americans" in the Corpus of Contemporary American English and glance at the results, you'll see that "we Americans" is almost always used in subject position while "us Americans" is almost always used in object position. Here is the screenshot for "we Americans": 

Here is the screenshot for "us Americans":

Prima facie, "we Americans" occurs in subject position, while "us Americans" occurs in object position. This supports the rule of thumb I described above.
That said, there is a convention in English regarding the modification of subject pronouns like 'I', 'you', 'he', 'she', and 'we'. These pronouns are allowed to appear as subjects pre-nominally modified by adjectives only if they are transformed into their object variant. For example, compare:

The drunk me is a nightmare.
The real her is better than the fake her.
Blonde him looks better than brunette him.
New York us is having a harder time paying the bills than did rural Iowa us.  

with

*The drunk I is a nightmare.
*The real she is better than the fake she.
*Blonde he looks better than brunette he.
*New York we is having a harder time paying the bills than did rural Iowa we.  

The reason the object pronoun is necessary may have to do with the fact that this construction is ultimately rooted in an ellipsis which requires it (for example, "the real version of me").
I suspect that the existence of this convention might lead some people to feel comfortable using "us Americans" in subject position. For example:

Us Americans love guns.

This is certainly acceptable in some dialects, although I haven't found any corpus examples yet. It certainly doesn't sound bad to my ear.
NOTE: I'm not saying that subject-positioned "us Americans" is the same kind of construction as "New York us" (syntactically, they seem to be quite different). All I'm saying is that the existence of the latter might influence a speaker's judgment regarding the former (it might lead him to think that the former is acceptable).

As a historical note, the linguist Otto Jespersen was probably the first to think about constructions like "we Americans." He treated them as involving appositional relative clauses that had undergone something like ellipsis (for example "we, who are Americans"). Postal (1966) argued against this analysis, as does Elbourne (2005).

