Originally Posted by TWA884

Unlike at LHR, there are no international-to-international transit facilities at any US airport. Every passenger arriving in the US on an international flight has to be admitted into the US and must clear immigration and customs inspections at their first port of entry. That is regardless of whether they connect to another flight, domestic or international. I believe that it is the same in Canada.

A few US airports, including DFW, IAH and MIA, but not ORD, have international to international luggage transfer. However, the connecting passenger still has to go through US immigration before boarding their flight to another international destination.

So, even if you connected in a different US city on the eastern seaboard, you still would have had to go through US passport controls when your transatlantic flight landed in the US. The only way that could have avoided going through both US and Canadian immigration and customs controls was for you to have flown non-stop to Toronto or with a connection at another Canadian airport.