I find the 40s, particularly the late 40s to be a time when our country was recovering from separations of families and had now entered into a period of reunion. The family unit grew strong in the late 40s and if you take a look at the 50s, the family was nearly perfect. Men worked, women cleaned house, cooked, and cared for the children. Family support of country and patriotism was high. Neighbors were not just civil, but neighborly.
I think her piece was a caution. Life had just become really good for so many Americans after about 15 years of pains with WWII and the Great Depression. I think she wrote to warn that life wasn't necessarily as easy as it appeared and you never know when tragedy is going to strike, or how close it will be to you.
If you read about Jackson's other writings, they all fit this same profile, normal life with a shock of impending doom.