Just look at how many wars and skirmishes the USA have been involved in since WW2 !
They seem to think they are the "world's police" and have the right to go in to every part of the world with their power and might.
In Vietnam they used Napalm, dropping it on villages and women and children. More here
https://www.warhistoryonline.com/vietnam-war/history-napalm-vietnam-war.html
They also used Agent Orange, a chemical to deforest huge areas so they could find people hiding under the forest and also destroy their food.
But this Agent Orange got into the soil and water and has caused deaths and birth defects and all sorts of other problems to hundreds of thousands of people.
Read about it here, you will be ashamed of the Americans when you read this
http://www.history.com/topics/vietnam-war/agent-orange
Sometimes you can understand why some "poor" countries "hate" the West when you see what we ("the West") have done all over the world.