I am not familiar enough with the situation in the North American continent to be able to comment on it.
As for the status of the European forrests in general and the German ones in particular, Spiecker was correct in his observations that there is more new growth than used to be. However, that is due to the fact that the more sensitive coniferes have gradually died over the last 40 years and the gaps they left are being filled with what I believe is called Hardwood in English (trees and shrubs with soft, wide leaves instead of needle-like ones: Dicotylendones).
That the deforrestation through acid rain has stopped is also correct. Simply for the reason, though, that all damaged trees have died by now and there are only such species left that are less sensitive to a low pH. Also, there has been a massive reforrestatiuon effort in the last decades, unparallelled in (German) history (2000 years after all). Last but not least the acid rain itself has become less (thank heavens! - pardon the pun).
This is a wonderful example how one can draw dangerousely inacurate conclusions from facts if one only looks at the results without questioning what lead to them.
'dangerousely inacurate conclusions'?
Hardly; my conclusion stands: The story of acid rain is not of catastrophe averted but of a minor environmental nuisance somewhat abated.
As you yourself recognized, for Europe there is more new forest growth than before, etc.
Your only point is that some of the more sensitive trees gave their place to better adapted species (do you have a source for the claim?). If so, this is darwinian evolution in action; as it has been throughout the evolution of life on earth.
All this is not even close to your alarmistic ~'we ruined the planet'.