While I'm sure that the US has a lot of great talent, to be sure. I'm skeptical of the fact that they could actually pull off the later stuff in Sailor Moon. I'm pretty sure they could handle the original Sailor Moon and a bit of Sailor Moon R... Sailor Moon gets a 'little' complex when S comes around.
Especially the Outer Senshi, and not just Haruka and Michiru. Setsuna Meioh/Sailor Pluto is a pretty deep character (Although, IMHO, Lucy Liu could pull off this role quite well.)... But I'm not so sure whether or not an American actress could pull off Hotaru Tomoe/Sailor Saturn. She's pretty darn complex for a girl her age.