Steel is not steel. There are many grades of steel. ....snip
And all grades of steel are in fact steel by definition suitability for a particular use is a different matter ....most of the metal assemblies are likely imported.
One can verify this by having an account at a particular site that gathers all bills of laden that pass through customs (they become public documents at that point) here in the US, this includes stuff offloaded in other countries but entering the US.
I haven't gone looking for Canadian imports but have a funny feeling such might be the case there as well TLHinCanada.