OTL McGovern won Massachusetts comfortably (it was a 9% margin) in what was basically a perfect storm against him. Even if Nixon pulls it off, there are no significant changes beyond McGovern becoming a trivia question, and the famous Don't Blame Me: I'm From Massachusetts bumpersticker never happening.
Reagan winning Minnesota in 1984 also just results in Mondale as a trivia question. There is no substantial difference between winning 49 and 50 states beyond bragging rights.
In any case, both McGovern and Mondale would win DC, so there would be no 538-0 wipeout.