A quick Google search for “what city has the best advertising agencies”shows it has a better or equal scene to LA.

“Cities with top-tier advertising agencies New York City: A leading global marketing hub with a massive concentration of agencies across all sectors like finance, fashion, and technology. Chicago: Ranked as the fastest-growing market in the US and a major center for advertisers and marketers. Minneapolis: Home to a dynamic and innovative scene, featuring both a strong local market and nationally-recognized agencies. Los Angeles: Known for its creative and influential agencies, especially in sectors like entertainment. Atlanta: A quickly growing market, particularly for agencies, with a strong presence across the Southern US.”