Demise of the subjunctive?

In many dialects of English, the indicative can take the place of the subjunctive, although this is considered erroneous in formal speech and writing. The similarity of the subjunctive and the past tense has led to the confusion between the two, and the error is evident in various pop culture references and music lyrics.
If I was President...
If he was a ghost...
If I was a rich girl..

However, in the context of the examples above, inversion cannot occur with the indicative as it would with the subjunctive; the following are ungrammatical, except insofar as they could be misinterpreted as questions:
*Was I the President...
*Was he a ghost...

Furthermore, many of the fossil phrases are often re-analyzed as imperative forms rather than as the subjunctive.

W. Somerset Maugham said, "The subjunctive mood is in its death throes, and the best thing to do is to put it out of its misery as soon as possible."

H.W. Fowler said, "Subjunctives met with today, outside the few truly living uses, are either deliberate revivals by poets for legitimate enough archaic effect, or antiquated survivals as in pretentious journalism, inflecting their context with dullness, or new arrivals possible only in an age to which the grammar of the subjunctive is not natural but artificial."

The subjunctive is not uniform in all varieties of spoken English. However it is preserved in speech, at least, in North American English, and in many dialects of British English. Some dialects replace it with the indicative or construct it using a modal verb (except perhaps in the most formal literary discourse).