Would it be nice, yes. Is it realistic to try and establish a captive population of every lemur? Unfortunately likely not. In the US we have Ring-tailed Lemur, the ruffed lemurs, Mongoose Lemur, and Coquerel's Sifaka that are at least reasonably widespread. We also have Black Lemur, Crowned Lemur, Red-bellied Lemur, Red-fronted Lemur, and the Aye-aye in some population. That's ten species, of which 6-8 are fairly viable. The Ring-tail and the two ruffeds are the best situated and fairly stable. It might be possible to bolster the Eulemur species by European imports, but there are two primary factors.
Most importantly would be garnering enough interest from zoos in the Eulemur. The Ring-tail and sifaka have been highly popularized, and the ruffed lemurs are flashy. Most Eulemur are not. In my experience Eulemur are either tucked away or mixed with other lemurs, rather than being showcased.
Second would be figuring how to establish successful populations without taking too many spaces from the other lemurs, since all of them are endangered. There would need to be a balance. Similarly balancing with other similar-sized endangered primates would need to be taken into account, for example the Francois' Langur.
I think it could be possible to boost the Eulemur in the US, but at the present moment I feel the likelihood of it happening is rather low.