Created using preliminary data on US births in 2014:
A few years ago the Census bureau announced that (non-Hispanic) whites no longer comprised a majority of newborns in the US, the implication being that in (less than) five years' time they would no longer constitute a majority of kids under the age of five, in (less than) eighteen years' time the would no longer constitute a majority of minors, etc.
Pew has a piece explaining the possible reasons for the premature announcement, though "wishful thinking" is conspicuously absent from among them. For the last three years whites have held the line at 54% of all births in the country.
In most states a majority of newborns are white. That is not the case in New York, Georgia, Florida, New Jersey, Maryland, Arizona, Nevada, Texas, DC, California, New Mexico, and Hawaii, however. Though the number of states is small, the number of people in these states is not, with the country's four most populous ones in the majority-minority column.
Politically, the Rubicon runs through Texas. When it inevitably flips from red to blue, the consequence will be 76 electoral college vote swing, ending any chance for a Republican to ever occupy the White House again. Florida is probably already forever lost to the GOP and Georgia is only a couple election cycles away from the same fate.
If you're of the persuasion that demography is destiny, there are two crucial determinants that shape the future: Immigration and differential fertility. These are the battlefronts.
In the interest of full disclosure, an indication of which side I'm on: