https://en.wikipedia.org/wiki/Operation_Freedom_Deal#Cambodi...
"Another impact of the U.S. bombing and the Cambodian civil war was the destruction of homes and livelihood of many people. This was a large contributor to the refugee crisis in Cambodia with two million people—more than 25 percent of the population—displaced from rural areas into cities, especially Phnom Penh which grew from about 600,000 in 1970 to an estimated population of nearly 2 million by 1975. The Cambodian government estimated that more than 20 percent of property in the country had been destroyed during the war."
https://en.wikipedia.org/wiki/Operation_Menu#Civilian_casual...
The bombings along with the landmines made it impossible to farm in many areas, which caused famine that then lead to the migration mentioned above. That's what I have heard from Cambodians that lived in those places at the time.
Also, similar events played out in Laos but the story is not as well known. More bombs were dropped on Laos even, and apparently in 2016 Obama allocated money to clean up a remaining 90 million pieces of unexploded ordninance.
https://www.reuters.com/article/us-laos-obama-uxo/u-s-gives-...
"From 1964 to 1973, U.S. warplanes dropped more than 270 million cluster munitions on the communist country, one-third of which did not explode, the Lao National Regulatory Authority for UXO says."