The correct answer is the mainland Southeast Asia, The mainland Southeast Asia is the region called "the land of great lakes." That is because the mainland has many amazingly beautiful lakes surrounding the country, besides, not just lakes but also rivers and oceans.
This is a very big question. Reason being, there were probably hundreds of effects of westward expansion. But, there are a few that come to mind.
1. Indian Wars
2. Economic Boom
3. Increase in Amounts of New Immigrants
4. New Issues Involving Slavery That Led up to The Civil War
5. Manifest Destiny Achieved
6. United States Increased Trade Opportunities by Being On Two Sides of North America
7. New Infrastructure Jobs
8. Gold Rush
9. Lawless Territories
10. Disease Spread From East to West
Turn around and look behind them.