We have no issues, because I was born in Scotland, so have a UK passport as well as Canadian. Helen has a UK passport too becasue she sleeps with me.
I have heard rumours of Americans ahving problems in N europe, but that enforcement si very las in S Europe, but that is all second hand info.
A few Americans we have met take the approach that they can get away with exceeding the 90 days as long as they do not try to fly into or enter the Shengen area, assumong that they will not be checked. Seems a bit risky to me, becasue we are checked randomly once or twice per year in docks or at sea by customs officers for VAT and smuggling checks , so I assume they would have counted out Shengen days too if relevant.
We are enjoying the 24 houir daylignt, specially sunny ones like last night