The legacy of the European welfare states can be traced to the end of WW2 where people were used to an extreme level of goverment involvement, rationing, controling all elements of industry for the war effort etc. After victory the cohesive spirit remained and people started wondering if it wasen't possible to use just a fraction of the resources devoted to war to better people's lives, and even to move to an advanced level of society.
Granted, it got out of hand some places with organised labour controling the economy and strangulating growth, but the mere notion that it is possible to build a better society is not a bad idea. Society should be ambitious, democratic and experimental in its organisation, just imho of course.
America never suffered the extreme destruction and deathtoll of mainland Europe and anti communism meant that successive progressive movements such as 'new deal' and 'the great society' never really took hold.