The IRS recently released Information Letter 2006-0025:
This letter responds to your letter dated November 4, 2005. In your letter, you requested information on whether Alaska and Hawaii, after their admission as States, are included within the definitions of “State” and “United States” contained under Employment Tax Regulation § 31.3121(e)-1. The simple answer is that Alaska and Hawaii are included within these definitions of “State” and “United States.”
Alaska and Hawaii are states. Who'd have thunk it?
Hat Tip to the Tax Profs Blog.