We're talking an administration which convinced itself that it could build a NEP-powered Pluto probe capable of achieving orbit in less time than it would take to get New Horizons there on a flyby; so we're hardly talking Rhodes scholars here. While the Prometheus time frame is almost certainly an exageration, it wouldn't surprise me at all if Bush & NASA have convinced each other that a nuclear propulsed mission to Mars would be cheap & easy to build; & therefore is a sensible retort to the PRC's LEO & Lunar ambitions. I doubt they will get much support outside the US, though - partly because few third parties will believe that the technologies can be made to work within likely budgets & schedules; but also because involvement in this will probably place ITAR limits on fully funded projects by the PRC et al.