the correct session is:
$_SESSION['WASF_CheckoutWizard_Basic_Default']['State']
so change this line:
if (true && (($this->GetTaxableTotal() > 0) && ((isset($_SESSION['eCartCheckoutForm_state_province'])?$_SESSION['eCartCheckoutForm_state_province']:"") == "NC"))) {
to:
if (true && (($this->GetTaxableTotal() > 0) && ((isset($_SESSION['WASF_CheckoutWizard_Basic_Default']['State'])?$_SESSION['WASF_CheckoutWizard_Basic_Default']['State']:"") == "NC"))) {