I personally believe that NATO expansion will be regarded as a bigger strategic blunder than the invasion of Iraq. First NATO expansion only reinforced Russian nationalism. When Gorbachev allowed those states in the Warsaw Pact to succede from the Soviet orbit, he thought that they would basically be neutral and unallied with NATO. However this did not prove to be the case and it only strenghened the position of hardliners in the Kremlin, who thought Gorbachev was wrong to end the Cold war. The end result was a Russia that is rightfully distrusful of the West. The second effect is that it once again turned Eastern Europe into a politically unstable region. Without the idea of NATO expansion in the early nineties, the Russians might have been able to pressure the Serbs to sign a ceasefire in both Bosnia and Kosovo. But because of their anger at NATOs move east the Russians were in no mood to help resolve the conflict in the Balkans and instead took to strongly supporting the Serbs. NATO expansion made the Georgian president believe that Georgia would be a member of NATO and would back him up in attacking that country's northern provinces. The inclusion of Poland into NATO could be explosive in that Poland favors the western Ukrainians over the eastern Ukrainians, who are backed by Moscow. So NATO could find itself in a dangerous  position should a Ukrainian civil war break out. Finally NATO expansion also has had a negative impact on events in China. The way Russia was treated after it introduced democracy to its citizens was to be punished and humilated by the West through NATO expansion, probably made a lot of reformist members in Chinese Communist Party and ordinary citizens rethink positions on political reform in China.  So far the foreign policy experts still believe that NATO expansion has been a positive development for America's strategic position in the world. The foreign policy establishment really needs to rethink their triumphalist view of the world.