When was the last time the white vote was more Democratic than the country as a whole?

[TDAS04]

1932?

Probably.

[TDAS04]

Either 1936, 1940, or 1944 if I had to guess. I know that either Lyndon Johnson in 1964 or Bill Clinton in 1996 was the last time the Democrats won the white vote overall. I recall reading that the only states where the Democrats won the white vote in 2020 were Massachusetts, Vermont, New York, Maryland, DC, Virginia, Illinois, Colorado, Washington, Oregon, California, and Hawaii.

Biden won the white vote in Virginia but not Rhode Island?

I forgot to include Rhode Island in my post.

You also forgot Minnesota, New Hampshire, and Maine.  There's no way Biden carried the white vote in Virginia, and he probably didn't in Illinois either.