You're assuming pursuit. For intercept you don't need a 180mph drone, you just need a somewhat predictable trajectory. You're also assuming constant motion away from shore or other ships, at top speed. Drones with speeds of up to 225kph (140mph) are already in use in Ukraine, although their payload is designed to take down heavy drones and helicopters (only a couple of pounds), and their range is only 12 miles. Nothing a month or two of rather straightforward scale-up couldn't fix. That's before we consider the practical scenario where a larger drone just drops these over the target. And if we assume the adversary is China, there could be hundreds of these larger drones in the air, with dozens of smaller drones each.