AHC: Extend the Sengoku Jidai by a century

Context: The Sengoku Jidai was a period in Japan, where is was near-constant civil war, social upheaval, and political intrigue from 1467 to 1615. It ended with Oda Nobunaga and Toyotomi Hideyoshi unifying most of the country, and Tokugawa Ieyasu taking over, and starting the Tokugawa Shogunate.

Challenge: Extend the Sengoku Jidai, the period in Japan, where various Daimyo fought each other for dominance over the land, by a century, instead of ending by 1615, ending around the mid-18th century or early 19th century
Nobunaga fails to ambush the Imagawa and gets slaughtered. Then Christian powers arrive and play the Daimyo off of each other.