But are they really?

[I]t is reasonable to say that the kingdom is the church, and the church is the kingdom—that they are the same even if they are not identical. They are the same in that it is the same people under the same King Jesus even if each term—kingdom, church—gives off slightly different suggestions. In particular, “kingdom” emphasizes royalty, while “church” emphasizes fellowship. Slight difference aside, the evidence I have presented in this book leads me to the conclusion that we should see the terms as synonyms.— Kingdom Conspiracy, page 206 (emphasis original)

<idle musing>
Not sure I agree totally with him here. Roger Olson is blogging his way through the book, too (part 1 and part 2). He has not yet come to this section, but before he began, he expressed his disagreement with an equation of the two: kingdom does not equal church. Maybe, given the caveats that Scot expressed here, Roger will agree, but I doubt it.
</idle musing>