SpaceX is reportedly seeking access to at least 80,000 cellular tower sites across the U.S. as it prepares to launch Starlink Mobile as a fourth nationwide wireless carrier. "We will be building out our terrestrial networks so there's broad-based connectivity anywhere that SpaceX and Starlink are allowed to operate," Musk said during SpaceX's earnings call this week. Satellite launches plus spectrum acquisition "will pave the way for Starlink Mobile to become a major mobile carrier in the US," he said. Bloomberg reports: One of the companies they're in talks with is Crown Castle, which, along with American Tower and Vertical Bridge Holdings, are among the largest owners of cellular towers.…