As the price of lumber goes up, there are more European imports coming into the east coast ports(Baltimore, Charleston, Savannah, New Orleans and Houston). My company brings containers of lumber from Europe into all of these ports. other companies bring in Radiata Pine from Brazil, Chile and New Zealand.
I can not think of any lumber from Canada that is brought into the US on a ship. It is all shipped via railcar, flatbed truck and enclosed vans.
It is more a function of the exchange rate between the US dollar and the foreign currency.
You want to help American companies? Cut the corporate tax rate and the capital gains tax. Deregulate. Get our government out of the way.
But don’t make doing business even more expensive. Don’t impose more taxes and barriers on American goods and services.