I've only heard folks call it black elderberry here.

Here is a paper that goes over the arguments for and against recognition of Sambubcus canadensis as a separate species:

Applequist, W. L. (2013, June). A brief review of recent controversies in the taxonomy and nomenclature of Sambucus nigra sensu lato. In I International Symposium on Elderberry 1061 (pp. 25-33).

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4859216/

While the main European and Eastern North American varieties have the same number of chromosomes, very similar pollen, and are potentially indistinguishable morphologically, they seem to be reproductively isolated not only geographically but also by the apparent general sterility of their hybrids.

Here is a quote from another paper paraphrasing part of the results of a different study:

"Seed set was obtained from the cross S. canadensis × S. nigra (Chia 1975). From 3 crosses, one produced 63 seeds and 2 seedlings, one produced 43 seeds and no seedlings, and one was sterile."

Atkinson, M. D., & Atkinson, E. (2002). Sambucus nigra L. Journal of Ecology, 90(5), 895-923.

https://www.researchgate.net/profile/Arvind_Singh56/post/What_is_the_toxicity_of_Sambucus_nigra_leaves_shoots_and_roots_Is_the_amount_of_cyanogenic_glycosides_in_a_given_speciman_variable/attachment/59d63d8579197b807799a50e/AS:420056862347264@1477160768899/download/1.pdf

Sadly, I can't access the study mentioned in the above quote, but here is its citation:

Chia, C. L. (1975). A chromosome and thin-layer chromatographic study of the genus Sambucus L. Diss. Abstr. Int., B, 36(4), 1565.

Still, the crossing data is a relatively small sample size. And there doesn't seem to be any good molecular phylogenetic studies that address the taxonomy of S. nigra.