It's quite surprising to see that large neosuchians preyed upon large theropods in Appalachia the latest Cretaceous, but the name "Struthiomimus" sedens you mentioned should be changed to "Ornithomimus" cf. sedens for now because the large ornithomimid specimen BHI 1266 was referred to "Ornithomimus" sedens by Carrano (1998) and Farlow (2001), who referred the species to Struthiomimus without detailed comment, and those authors don't explain why BHI 1266 is the same species as the sedens holotype USNM 4736 or why sedens belongs in Struthiomimus. Claessens et al. (2015) redescribed the Ornithomimus type species, O. velox, and BHI 1266 is yet to be described in detail, so it's possible BHI 1266 could represent a distinct taxon generically distinct from Struthiomimus because McFeeters et al. (2016) recognized one putative Struthiomimus specimen as a distinct taxon, Rativates evadens.
Carrano, 1998. The evolution of dinosaur locomotion: Functional morphology, biomechanics, and modern analogs. PhD thesis. The University of Chicago. 424 pp.
Claessens and Loewen, 2015. A redescription of Ornithomimus velox Marsh, 1890 (Dinosauria, Theropoda). Journal of Vertebrate Paleontology. e1034593 DOI: 10.1080/02724634.2015.1034593
Farlow, 2001. Acrocanthosaurus and the maker of Comanchean large-theropod footprints. In Tanke, Carpenter, Skrepnick and Currie (eds). Mesozoic Vertebrate Life: New Research Inspired by the Paleontology of Philip J. Currie. pp. 408-427.
McFeeters, Ryan, Schroder-Adams and Cullen, 2016. A new ornithomimid theropod from the Dinosaur Park Formation of Alberta, Canada. Journal of Vertebrate Paleontology. 36(6), e1221415.