I know things like this ebb and flow but I think the education system and leftist leaning of educators are taking hold. I know I went thru a period I wasn't 'very patriotic" primarily because of stateside reaction to the military due to Vietnam --even though we had a draft and theoretically all could be required to serve but got over it. Now I think it is educationally and politically driven
http://hotair.com/archives/2017/06/30/poll-third-millennials-say-theyre-not-patriotic/