Doesn't the EU already have very high tarriffs on a lot of things imported from the US? Cars for example?
Harley Davidson was one of these companies. They weren't doing well before they got caught in the middle of this trade war, since the "biker" culture it aimed at was shrinking globally, so in a move to survive they decided to move production to South America. Turns out their audience didn't like this move, and its death accelerated.
TL;DR: Trump put a tax on European steel, and the EU snipped Harley Davidson in retaliation.
Their stock price (even over five years) doesn't appear to reflect this.
Their stock price today is around 30$. In the early 2000s it was around 90$.
Also, like the other comment mentioned, HD has been playing a lot of financial tricks over the last 20 years to prevent the stock price from declining (e.g. buy backs to artificially inflate stock price, take a look at the number of outstanding shares: https://www.macrotrends.net/stocks/charts/HOG/harley-davidso... , a reduction from 280 million to 150 million in the 2005-2019 time period).
EDIT: I recommend https://www.youtube.com/watch?v=EOwxxsPaogY for a summary.
HD decision of focusing their brand on a "hardcore biker" culture that has failed (and arguably even alienated) younger customers is what killed the company.
All customers age, but what HD has failed to do is attract new customers at a faster rate than the death rate of their current customers.
They sell a little under a million units a year there.
https://www.statista.com/statistics/642946/eu-ford-car-sales...
Ford is pretty heavily involved in Europe. Cars are bigger in Europe, so Ford cars tend to be developed there, while trucks and SUVs are bigger in America, so design of these vehicles is largely done in America.
https://www.best-selling-cars.com/europe/2019-full-year-euro...
This is a function of our China policy and insistence on maintaining the dollar as the world’s reserve currency.