Only in the United States. I assume that the rest of your dates are for the U.S., and not the global values?
Anyway, sea ice is influenced by more factors than temperature, though temperature is important. And the values look pretty constant, so it would be hard to discern an overriding temperature influence, I would think.
Ok, 1945 was a particularily warm year by global standards.
And 1957 was an espscially cool year.
Yet your graph shows no change.
And by your own admission, sea ice is not a good indicator of average atmospheric temperature.