The only place I can find that claim regarding the USA is TVTropes, I suspect it is simply good taste that keeps the symbol off toys here... When I go to the Revel model site I see some model planes featuring the symbol. The site has a separate German section and those planes do not have the symbol... So I think ElAurens is right (it's not our fault!!)
The only law I know of in USA is New York (I think) a swastika used as graffiti is a felony.