I think camera bodies make a much larger difference these days than lenses, actually. Obviously the lens still makes a notable difference, and for certain forms, like wildlife photography, the lens requirements are inescapable. The new models out in the past few years have absolutely incredible low-light performance that completely change the lens landscape, even; you can now ditch the requirement of carrying a hefty f/2.8 400mm lens around and swap it out for a lightweight f/4 with a camera that more than compensates for the light loss.
But with the capabilities of modern cameras the production requirements for them are high and the challenge to make something that works for a variety of consumers even higher. I can't even look at a camera that isn't "weather-proofed" as I live in a place with a 90% chance of rain at any moment, for example. And a lot of these advancements are designed to work in combination with the lenses, such as in-body and in-lens stabilisation working together, weather seals that line up, etc. I think it's pretty important to maintain the same manufacturing quality between the two areas. I'm sure that's possible when moving production to Thailand, but I expect it will take time for them to iron out their processes.
My personal experience of Canon vs Nikon is that I prefer the software of Canon, and historically I preferred the physical ergonomics of Nikon, but the newest Canon models have improved a lot there. On the lens side it was always Canon for me, although I do have a lot of love for Sigma: my 150-600mm Sigma lens has a USB dock where I can actually manually configure the autofocus, among other things, which appeals to my gadget side (and honestly their quality has jumped up massively in the past decade).