Decades of American Dream, Shining City On The Hill, Land Of Opportunity type propaganda. Plus the fact that you did/do have plenty of people trying to immigrate and seek a better life in america (because america/it's proxies/other imperial states wrecked their home country but they don't focus on that)

Plus that kind of boomer has rarely travelled outside their comfort zone or met people from different walks of life so they can't comprehend why people wouldn't want a 40 year mortgage on a suburban home, 2.5 kids, a lawn, suv, 2 hour daily commute, and zero community