LOL LOL LOL
There is NO chance an American company is going to come here, ever. Not because of the oligopoly's power, but because it's not worth their time. One of the last business cases I was a part of when still in the industry was analyzing the threat of Verizon entering in the Canadian market. The end result was slim to none. The business case was -$2 billion to them lol.
A U.S. company can either try to get 5M extra subscribers on their home base of 300+ million people or can enter into the Canadian market and struggle to get 5M people on a base one-tenth that size, while incurring massive upfront costs of buying spectrum and building out its network (unless they wanted to go the MNVO route which would be slim to none), and marketing to a new place, including needing materials and customer service in French. So what route do you think they will take?