https://twitter.com/p_millerd/status/1118071142311288838
Highlights:
"After some digging I found the 2016 appendix (again, 2017 not to be found). Only 12% of people couldn't actually pay the expense"
"Another survey question not highlighted actually gives some direct clarity on this question. It turns out only about 15% of people would not be able to cover a $400 expense [without impacting their ability to pay other bills]."
Note that "12% couldn't actually pay" is about equal to the 2017 official poverty rate of 12.3%. I don't find it surprising that people counted as "in poverty" would have problems covering a $400 immediate cash expense.