[…] has been some attempted pushback – including in the comments here – on the notion that Donald Trump has uniquely damaged German-American relations, […]

I don't know where MK Bhadrakumar gets his stats - possibly Russia Today: https://www.rt.com/news/germany-lose-trust-us-snowden-431/ - although RT gives the date as 2014. Die Welt, just to provide one quick example, reports a decline of 37% on the same question from November 2016 to the Feburary, on 70% distrust vs 22% trust. Certainly there was decline from Obama's first year over the course of his term, with some notorious incidents - especially around the Snowden affair - punctuating and deepening it. If you really want to examine German public opinion,

https://www.welt.de/politik/deutschland/article161766668/Deutsche-verlieren-wegen-Trump-Vertrauen-in-die-USA.html (The decline numbers are the ones in parentheses after each country name.)

I'll be posting a quick rundown on the recent history of that poll.

...Mrs Merkel’s comments today illustrate how much Trumpandbrexit has hurt America and Britain in the past months.

From M.K. Bhadrakumar's take on Hausfrau Merkel's remarks:

By the way, this has nothing to do with Trump. The percentage of Germans who trusted the US plunged from 76% to 34% during the first six years of the Barack Obama presidency.