Alaska's carrier-screen role and Iowa's response force

Were the Iowas built to counter the Kongos as carrier escorts?

No; Alaska better fits the carrier-screen role, while Iowa belonged to the fast battle response force.

Alaska could defeat smaller surface ships and delay a larger attacker that surprised the carriers. The carrier group would withdraw while the large cruiser fought to buy time. Carrier aircraft could keep attacking as the Iowas approached as a fast battleship response force. Alaska might be lost before that force arrived, but its delaying action could still let the carriers escape.