Buy European

"It remains questionable how much influence civil boycott campaigns have". Does it really? I'd say it mainly depends on how many people join it (i guess that's the questionable part). Nothing runs without the population at large. It's hard to win a trade war when the enemy population hates your country, while your own population is largely indifferent to the enemy country.

Even if people only switch half the american products they consume to products of other origin, that can be pretty significant. For once I'm fully on board with this and will try to convince people i know irl to also switch to non-US products, if nothing else for those where it doesn't matter much to them anyway.