Also called "dumping".
uslumbercoalition.org
The truth is that Canada doesn't want Canadians to share in the lumber wealth they have which would reduce the cost of housing and encourage population growth. Canada would prefer to remain a small, elite, gated, country.
Text excerpt from your link clarifies some of the issue;
...
U.S. Lumber Coalition: Dumped and Subsidized Canadian Lumber Import Forcing American Lumber Companies to Reduce Hours of Operations
Washington, D.C., February 11, 2025 – The American lumber industry sits on its highest excess capacity since the Great Recession — capacity that could be used to produce more lumber to build U.S. homes. Meanwhile, Canadian dumped and unfairly traded lumber imports are trending up.
“The recent rise of unfairly traded Canadian lumber imports has yet again put tremendous pressure and hardship on the workers in the U.S. forestry industry,” stated Andrew Miller, Chairman and Owner of Stimson Lumber. “Canadian companies benefit from the strong support of their federal and provincial governments who are willing to do anything it takes to maintain artificially high market share for Canadian lumber in the U.S. market,” added Miller.
“Canadian lumber producers’ continuous unfair trade practices are forcing idling and closures of U.S. lumber mills. This is why the U.S. lumber industry applauds and strongly supports President Trump’s unyielding stance on fully enforcing the U.S. trade laws,” stated Steve Swanson, Chairman of Swanson Group.
“We strongly agree with the statements by Secretary of Commerce nominee Lutnick that foreign countries like Canada have taken advantage of our markets and that this needs to stop,” added Swanson. “Canada must cease treating the United States as a dumping ground for its excess lumber production, which amounts to a Canadian jobs program at the expense of American workers, their families, and forestry dependent communities,” concluded Swanson.
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Quid pro quo tariffs will either balance the situation and/or encourage some re-negotiations.
However, as pointed out here and on other topics*, the USA has been subsidizing the rest of the world long enough. Time we reduce our $$$ outflow and other nations pay their real and fair costs rather than have Uncle Sugar do it.
* Such as NATO and the UN.