Here's my map of how this matters, based on the 'trend' number in your graph and the relative share of the white vote in the state:
Wisconsin, Michigan, Ohio, and Pennsylvania all have the potential to become problematic for the Democrats if this white trend continues. Montana is moving further out of reach, and in Arizona the white vote has the potential to quite easily counteract Hispanic increase with increasing GOP white majorities, for a long time to come.
By contrast it is excellent news in New Hampshire, Iowa, and Maine - they're becoming more reliably Democrat. At the same time Virginia's and (down the road) North Carolina's status as Democrat-leaning states due to increasing minorities and an influx of liberal whites is in no way counteracted by any 'existing white backlash'.
Finally I colored Georgia, South Carolina, and Texas green as they have a high potential for changes in white voting behavior to either counteract or fail to counteract increases in minorities - we really need figures on those.
On the whole I'd say the original poster's map shows the white situation is pretty harmful in almost twice as many electoral votes as it is helpful, though probably electorally irrelevant in most of the country as it won't change the outcomes.
