That's like saying G.I. Joe isn't really "West" because it was co-produced by Toei.
Yes and no. Transformers figures began as Japanese toys (mostly created by Takara), as opposed to G.I. Joe toys, which purely originated within the U.S. TF certainly holds a stronger presence in Japan and has a much more "native" feel (thanks also in no small part to numerous Japan-only/Japan-initiated iterations of the brand). Taken strictly on the merits of the original TV show, though, the Toei co-production wouldn't be enough, true.
Does this really count as East Meets West given that Transformers was originally co-produced by Takara-Tomy?
Technically speaking, Japan first created the toys with both of Takara-Tomy's toy brands: Diaclone (Optimus' toy origin) and Micro Change (Megatron's toy origin). Here, we can say that the Transformers as a franchise hasn't existed yet. Then Hasbro acquired the toys and sold them all under one brand name. Here is when we can say is the birth of the Transformers as a franchise, since the cartoons and the comics both originated in the US. Takara then imported the cartoons and the comics to Japan, and some can then interpret this as East Meets West. In the meantime, Marvel imports Transformers to the UK, iirc