I need a word for "impotent whining"

"Hand-wringing" is used to express the idea that someone is "fretting" over something and instead of taking positive action, just stands by, impotently wringing their hands.

Hand-wringing as defined by MWO:

an overwrought expression of concern or guilt

This expression dates back to 1922 (per MWO).

I think the word moping works.

Mope:

To be unhappy and unwilling to think or act in a positive way, especially because of a disappointment.

'There's no point in sitting at home and moping - get out there and find yourself another job!' (Cambridge Dictionary)

‘But he frequently has been his own worst enemy by moping and overanalyzing, leading to a loss of confidence and bad habits.’ (OED)

There's always the British "whinging," which I think of as "extra-strength whining". (Also, with respect to the Trunp presidency, I think "grieving" may be what you're observing in others.