Jose Padilla was Hispanic. John walker Lindh and Richard Reid are Caucasian, a native-born American and a native-born Brit. The members of the Portland cell, with the exception of one member, were black native-born Americans.
I don't think it's safe to assume that profiling will necessarily help. Certainly the higher percentage of al Qaeda trainees are Arabs, but a smart terrorist group would compensate by training non-Arab types as well, which they obviously have done.
In Bush at War the randomness of airport checks is explained as an effort to snag people like this.
And then there are Chechens and Tajiks, etc. They are as bloodthirsty as the Arabic terrorists and do not have arabic-sounding names.