Of relevance is the following:
It should be self-evident, however, that such a result is absurd, and cannot have been intended.
Congress cannot possibly have meant to treat individuals who had long since relinquished their U.S. citizenship, and whose expatriations had always been respected for federal tax purposes, as if they had been citizens all along.
Undoubtedly, Code Sec. 877A was meant to apply solely to individuals that, on (or after) the date of enactment, were otherwise treated as citizens (or long-term residents) for federal tax purposes.
Any individual who took all steps required to successfully terminate citizenship for federal tax purposes, under the tax laws as in effect immediately prior to enactment of the 2008 Act, would not again need to relinquish U.S. citizenship and thus could not be within the intended scope of Code Sec 877A(g)(4).