I think for a presidential candidate to engage in a school child’s rendition of an Asian accent while on the campaign trail should qualify as racism by negligence at least, if not by actual commission.
I mean, most presidential candidates have enough adults on staff that they avoid this kind of crass bullshit – they’re at least sensitive enough to the possibility of accusations of racism to avoid them (or to engage in some degree of circumlocution).
The fact that Trump doesn’t bother is, I think, meaningful and perhaps even worthy of discussion (assuming anything about Trump is actually worthy of discussion).