What is your evidence that they are scared rather than disinterested?
Also, in what way can an organisation said to be scared? If you mean it metaphorically, what is do you mean literally?
Nope, not a bit. They made it fine before without them and are already cooperating with them (and several other countries) on the ISS.
Russia has already missed several critical delivery dates on ISS stuff and NASA doesn't want them messing up like that on the Moon mission. They just don't want the trouble.
I think they are scared that in 15 years NASA fakes missions will be exposed.
Russia, China, Japan, India; All are going on moon. So it will become clear what the real thing look/feels like, if these countries actually attempt these missions.
Hence its important for USA to reach moon again to save their noose.