Los Angeles is the nation's second-largest city. So it's not unreasonable to expect that presidents will, on occasion, visit it.
Los Angeles also has terrible transportation problems, and has for decades -- and the solutions all involve stuff conservatives fight: taxes, building more roads via eminent domain, public transportation, rail, subways, bike lanes, etc.
And yet, conservative partisans -- who resist all of the above remedies to L.A.'s transportation problems -- blame Obama for the awful traffic every time he visits. (h/t Putz.)