Mothership 

An alien mothership arrives in Tianjin in 2025.

30 million Chinese are killed.

International teams of military and medical personnel are sent to China to investigate. Rumours abound about what is happening in China, especially Shanghai.

After 2 years, the mothership begins to move west and starts destroying parts of Europe, eventually arriving at New York. The Mothership continues moving westward and destroys parts of California. The mothership proceeds to circle the earth, with countries experiencing attack from the mothership roughly once every 2 months, with each attack lasting no more than 2 hours. 

List of Affected Cities and States:

Tianjin, Beijing, Islamabad, Kabul, Tehran, Istanbul, Belgrade, Zagreb (Croatia), Salzburg (Austria), Munich, Stuttgart, Frankfurt, Paris, Brussels, London, Dublin, Montreal, New York, Toronto, Detroit, Chicago, Milwaukee, Iowa, Nebraska, Denver (Colorado), Las Vegas, Los Angeles, Tokyo, Seoul.