Check out this graph. If you can't read it, go to this link where it's much larger.
This chart plots the years between 1915 and 2015 and adds the number of years the US has been at war. For example, I was born in 1944 -- the US has been at war for 43% of my life. For anyone born between 2001 and 2015, the country has been at war 100% of their life.