I do not think that is primarily because of Canadian carriers suddenly rushing into the U.S. market and taking over the U.S. market. It is probably more of a concern that, if cabotage is allowed in Canada, it would be difficult not to allow it for carriers from Europe or from Asia, and they could have a much bigger impact on the market.
Je ne pense pas que c'est principalement par crainte que les transporteurs canadiens viennent envahir, mais s'il l'on autorisait le cabotage pour les Canadiens, il serait difficile de le refuser aux transporteurs d'Europe et d'Asie qui auraient un impact beaucoup plus grand sur le marché.