The USA under him have done fairly well - qualified for the World Cup with ease (although their zone isnt too tough), did very well in the Confederations Cup (beat Spain and nearly beat Brazil in the final) and set up his defence to completely nulify Rooney at the World Cup, although they were disappointing against Ghana. Arguably you could suggest most managers would have done equally as well.
I dont think it'd be a bad appointment in terms of the stuff I posted above, but he has no experience of a proper transfer market (the MLS runs differently) and he hasnt managed any team outside of the US.