Hasn't that always been the accepted gringo pronunciation? In Spanish, "Los" should have a long "O" sound, but I grew up there decades ago, and it was always pronounced the same as "Las Vegas." In fact, people of my father's generation (fought in WW2) often pronounced Angeles with a hard G - like the English word "angle"...sounded like "Las Angle-us."
Americans have always murdered Spanish. The one that used to bug me the most when I lived there was "Lah Pewenny" (La Puente) and "San Peedro"....though "San Paydro" is just as wrong.
Up here in the Bay Area, the Silicon Valley is headquartered in "Sanazay" (San Jose), and there is the suburb of "Sallyandro" (San Leandro). People up here refer to the '89 Earthquake as the "Loma Pre-ayta" earthquake (Loma Prieta). Drives me nuts, and I'm not Latino, and my Spanish sucks.
My old radio prof always referred to LA as "Las Angle-us". He was 59 in 1973 and was Don Ameche's announcer in Hollywood for three years. He was PD of KGW/KEX when they were the Red and Blue network afilliates respectively.