Here is the AOU's written policy on English names from page xiii of the 7th edition.
When a species was divided into two or more distinct species, we have used former English names, if available, for the resultant taxa. In general, we have followed the policy that no English name should be used for both a combined species and one of the components (Groups). However, we often have retained a well-known English name for a widespread North American form when a taxon that is either extralimital or restricted in distribution is separated from it. An example is the retention of the name Red-winged Blackbird for Agelaius phoeniceus when the Cuban population was separated as A. assimilis and named the Red-shouldered Blackbird.
Perhaps I don't understand, but it sounds to me like the Pacific Wren is comparable to the Red-shouldered Blackbird in distribution, allowing retention of "Winter Wren" for the widespread North American population.
Trying to avoid another Mel Gibson lapse here, but it's not easy.