Meta Platforms Inc.’s Instagram will soon account for half of the company’s advertising revenue in the US, according to estimates from research firm Emarketer, further cementing the photo- and video-sharing app’s role as the key growth driver for the company.Instagram has steadily expanded into arguably the most important part of Meta’s business, not only for its role driving revenue but also as a vehicle for features like Reels and Threads that offer competition to rivals. In 2021, Instagram ge...