TWENTY YEARS AGO, Europeans were savaging Reagan for not being nice enough to the Russians, and for pursuing an arms buildup they were sure would lead to nuclear war. Now, with the Soviet Union gone and Russia joining NATO after a historic nuclear arms-reduction treaty, they’re bowled over by the brilliance of American diplomacy in achieving such a bloodless triumph, and embarrassed that they ever could have doubted us. Uh, aren’t they? Well, no. . . .