That looks like a boring map.
What makes a map challenging or interesting in Mini Metro is where the bodies of water is placed and shaped. What kind of network is already the city (if any) doesn't affect anything.
Los Angeles (pop. 4 m) seems to have 8 lines; but no water (except the edge of the map), which makes it even easier than London currently in Mini Metro.
Stockholm (pop. 1 m) has 3 lines; with several islands in the center of the map, and two landmasses north and south. This would be a highly challenging map ... for the most experienced players.