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.
- *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).