Yes, actually, it would. Why? Because foreign policy is the responsibility of the executve branch. The president is our Chief of State as well as our Commander in Chief. One need only look to Bill Clinton's monumentally (if not criminally) negligent handling of this nation's foreign policy, which directly resulted in, among other things, the 9/11/01 attacks, to understand the danger Kerry (and all Leftists/Democrats) poses to all of us.
For other examples, look to the Johnson administration's ratcheting up of our involvement in Viet Nam, followed by its failure of the nerve and will necessary to win the war. Look to Carter's pathetic foreign policy which led, among other things, to the fall of the Shah of Iran, the rise of Ayatollah Khomeini and of Islamic radicalism.
George W. Bush is the only U.S. president to take the action necessary to begin to turn the tide of Islamic radicalism. In doing so, he has reasserted U.S. sovereignty and right of self defense, and basically told the "international community" (i.e., international Left) to go pound sand. (It's really why they hate him so much, in case you haven't figured it out.)
President Bush's defeat would be seen by the Left, the Osama bin Laden's of the world, and even Republican elected officials here as a repudiation by the American public of all that GWB has been able to accomplish in defeating radical Islamism and separating the U.S. from subservience to the international Left. As a consequence, a Kerry presidency would reverse all the good President Bush has been able to accomplish. Kerry's weakness would embolden the terrorists just as Clinton's weakness did. In fact if GWB is defeated this November, it would be a monumental defeat for the United States in the War on Terror.
This nation cannot afford another 9/11 or worse, a series of such attacks. But Leftists like Kerry wouldn't care, becase the Left wants this nation hamstrung, if not fully disolved.
Maybe "real" conservatives are suicidal, so they won't mind a Kerry presidency, but I'm not. For me — and anyone else with even an ounce of common sense — it's GWB all the way.
Also, I've pointed out elsewhere that the next President will likely make four nominations to the US Supreme Court. If that President is John Kerry, we can kiss the conservative movement good-bye, as Kerry will shape the nature of the federal judiciary for the coming generation. If Kerry makes those appointments, we'll all be dead before there's another conservative majority on the Supreme Court.