Markets have been focused on the day-to-day drama in China's stock markets, but when it comes to the long game, the focus should be squarely on the United States and other developed markets, Brian Belski, chief investment strategist at BMO Capital Markets, said Wednesday.

"What we have to think about from an investing standpoint is the last 15 years was about [emerging markets], China, anything but America. The next 10 years, maybe 15 years, is going to be about American and developed market growth. Period," he told CNBC's "Squawk Box."