> It seems to me that ICE agents who wear masks are
> more embarrassed than fearful of identification.

Third possible motive*: increased intimidation factor. I leave enumerating examples as an exercise.

.... Hm: Washington State in the north; California in the south. Might the entire western seaboard of the US be up for (eg) going in with Canada :-) ?

* Not that these motives need be unmixed, mind you.