I think the redesign of the NES shell for the North American market was largely for vanity reasons, wasn't it? Entertainment system instead of computer, grey plastic instead of beige, front loading instead of top, long cartridges that were supposed to look like VCR tapes instead of toys.
My understanding was that after American retailers were burned so hard by the Atari crash, Nintendo wanted to position the NES as far from a 2600 as possible.
N also took the opportunity to remove the lockout chip, since the system came out so late in the lifecycle and they were largely successful at stamping out unlicensed releases.
The Japanese version of that redesign also got compatibility with existing SNES Multi-AV cables (at least the composite ones, the AV Famicom didn't output s-video) while the US version was RF-only (and AFAIK is worse for jailbars than any previous NES)