(Aside: I still remember being in school discussing geopolitics with my fellow third graders. We concluded that the duck-and-cover drills were worthless and were being done so the adults could feel like they were doing something. We knew we could not survive nuclear war by hiding under a desk and even if we did we wouldn't want to.)
The current stimulus for the United States placing (defensive) missiles in Poland is the 2008 Presidential election (the Russian action against Georgia is a red herring). The White House is hoping to generate an international crisis with Russia that McCain can use to campaign for the need for a warrior president.
If this campaign tactic leads to war, well, that's just the price of victory.
John McCain will do anything to win election, even starting a war with Russia.