The level of play in the USA has increased. That is true. HOWEVER, the number of quality players has also increased. That means the pool of talent available to the OHL has increased as well. So, even though there are more top prospect type US born players choosing to play in the USA, there are still more US born players suiting up for the OHL.
As the quality of the talent in the USA increases and the pool of quality players increase, the teams down there are less likely to support Canadian born players playing in their leagues. That means less opportunity for Canadian players. At some point, the USA will produce more hockey players than Canada. It is inevitable. I wouldn’t worry about what you are getting at for the long term.
The pressure point is the cost of hockey in general. It is out of reach for most people now, or at least for the elite programs that produce the players that make up Major Junior and Pro hockey leagues. Until they tackle that issue, hockey in Canada will remain stagnant. They can’t raise the bar anymore at this point without making it more affordable for families without the means of dumping $10,000 to $20,000 or more per year for elite programs. Multiply that by 5-8 years and you have $50,000 to $160,000 to put a kid through elite programs from age 8ish to 15. And when I say $10,000, that is lowballing to the extreme.