While I initially thought that this was Aciurina bigeloviae (see discussion here - https://bugguide.net/node/view/381337 ) after dissecting several of these Ericameria nauseosa galls, it is clearly a different gall, namely a polythalamous cecidomyiid gall. Each gall contains several sacs containing cecidomyiid larvae (ided by obvious bright orange color and peripneustic respiratory system).

Most of the galls have thin, bract-like leaves around the base (picture number 2), but the older ones seem to have lost this (e.g. picture #1)