Originally Posted By: duncan7
The NCAA, at least, seems to capitalize the first A and they ought to know.

The NCAA is handing out what are basically titles which should be capitalized, e.g. just because someone says "Coach of the Year" doesn't mean coach or year should always be capitalized.
Even so if you search for "all-american" on their site, you can see they use it both ways.
"2005 NCAA discus champion and four-time all-American in the discipline"
and
"GTE Academic All-American Volleyball Player of the Year"