You have probably heared about the attack on the US embassy in Athens, Greece. There has been some attacks against US-interests in Greece during the last years but it´s not something most people in Greece think is okey. The attacks are most likely made by people in leftwing groups and as far as I understand it, they are not a threat to americans in common. People know that many americans are against the war so I don´t think that many see american civilians as targets.
As for Turkey, yes, the biggest problems are far away from where you will be but it has been attacks on places with lots of tourists too.