This insect is now the commonest Sceliphron in Southern France, where it began to be commonly encountered during the late nineties. Before that, two native species were fairly common, but are now very rare or even extinct locally.
I agree with Mr. Eaton that this species is strongly variable as for the amount of yellow, even on the legs. For example, many specimens found in France lack the yellow spots on the propodeum and on the first abdominal tergite - or have much smaller ones than this brightly colored male. Moreover, I never found any specimen with a yellow petiolus, like this one. This suggests that the population introduced into Europe came from a more Northern region than NC.

This is indeed a black and yellow mud dauber. The extent of yellow markings is highly variable, even from individual to individual.