Bradford’s giant, map-like collage works were already among the best painting being done in the country. Then in 2008, he made two works that channeled the anxieties of the post-Katrina, late-Bush-Administration years. The first was “HELP US” scrawled in giant letters atop an LA gallery. Next, he built a 64-foot-long arc from recycled construction-site barricades for a biennial in New Orleans. No wonder the LA artist, whose first survey now arrives at the ICA, won a MacArthur “genius” grant last year.