Industry representatives were reluctant to comment publicly, with several saying it was too early to know for certain how they would be affected by the US tariffs - as well as the retaliatory measures introduced later in the day by the Trudeau government.
The tariffs will impact directly on Port Talbot as around 10% of Tata Steel Europe's exports go to the US.
In Europe, there was disappointment, but less surprise.
He says the US action leaves the European Union with no choice but to proceed with a case in the World Trade Organization.
"This is not the way we do business, and certainly not between longstanding partners, friends and allies", EU Trade Commissioner Cecilia Malmstrom said in a statement.
The EU has threatened tariffs on Harley-Davidson motorcycles and bourbon, measures aimed at the political bases of US Republican legislators.
British officials appeared the most alarmed.
Following the U.S.'s surprise announcement of the tariffs on steel and aluminium earlier this year, the European Commission warned of the possibility of retaliatory action in the forms of tariffs on USA imports to Europe such as on Harley Davidson bikes, and Levi's jeans.
Canada, the largest supplier of steel to the United States, will impose tariffs covering C$16.6 billion ($12.8 billion) on imports from the United States, including whiskey, orange juice, steel, aluminum and other products, Foreign Minister Chrystia Freeland said.
The U.S. decision came despite last-minute talks in Paris this week to try to reach a deal.
The EU is set to take action against the United States at the World Trade Organisation, while imposing duties on American imports expected to include orange juice, peanut butter and other goods. That summit is likely to be a frosty affair, much like last year's in Taormina, Sicily.More news: Spanish PM faces defeat in no-confidence motion
More news: Russian Journalist Shows Up to Dispel Reports of His Own Murder
More news: The euro is sliding amid political uncertainty in Italy
With a week to go before the June 7-8 summit, there's still no final agreement on the agenda, British and Italian officials said. Trudeau responded that there was no way any Canadian prime minister would sign a NAFTA deal that included a five-year sunset clause, and the visit was scrapped.
Mr Trump has the authority to lift the tariffs or alter them at any time, he added.
German reaction to the announcement of the tariffs was among the fiercest. Manfred Weber, a key ally of the German chancellor and leader of the biggest bloc in the European Parliament, accused the Trump administration of treating American allies as enemies.
George said it's unclear whether the tariffs are a negotiating tactic on the part of USA officials. "Europe does not want a trade conflict".
The problems of steel dumping will not be solved by unfair tariffs, and steelworkers in the United Kingdom and U.S. must not fall into the trap of believing rhetoric from the likes of Donald Trump.
George said Canada will still work in good faith with the US on renegotiating NAFTA, as it's critically important for all three countries to come out of negotiations with a deal that benefits all parties.
Some countries - including Argentina, Australia, Brazil and South Korea - agreed to restrict exports of metals and were exempted, but Ross said the EU, Canada and Mexico were not there yet.
The NAFTA talks were one factor in the administration's decision to grant exemptions to Canada and Mexico from the steel and aluminum tariffs.
"Economic nationalism leads to war".
The row has revived fears of a global trade war.
"Today is a bad day for world trade", she said.
The United States confirmed steel and aluminium tariffs would be levied on imports from long term allies Canada, the European Union and Mexico.