The focus on the breakout in U.S. stocks is overshadowing an equally important event: a global stock market breakout. While the U.S. is up roughly 3 percent for the year, the rest of the world is outperforming, including emerging markets, Japan and Europe — up 9 percent, 5 percent and nearly 5 percent year to date, respectively.

Large regional ETFs are also hitting new 52-week highs, including Latin America, the Pacific, emerging markets and, most notably, Europe.

What's behind the outperformance? Consider:

Global earnings estimates for the iShares ACWI, a basket of stocks representing 23 developed and 23 emerging markets, are expected to rise 13.1 percent this year, outpacing expected gains in the , according to Bank of America/Merrill Lynch.

JPMorgan and others have also noted that the global profit cycle has improved: "A central tenet of our global outlook is that the deflationary shocks weighing on growth over the past two years are unwinding and will produce a profit rebound that revives business capital spending." Goldman Sachs has noted that higher inflation was underpinning a global "reflation trade." That has pushed the stock markets of commodity-oriented countries, such as Chile, Peru, Brazil, Australia and Canada, to new highs. Barclays revised its growth outlook for Europe upward, noting that business surveys are pointing to acceleration in activity despite political uncertainty. European companies are growing earnings for the first time in years.

What could keep the rally going? Upward revisions in earnings growth, for one, starting with the United States. Bank of America noted that while 2017 guidance from U.S. corporations has been typically tepid since they want to set the bar low, the commentary on conference calls has been far more optimistic — literally. The word "optimistic" was used on a record 51 percent of the calls BofA monitored this quarter, the highest since they began monitoring this data in 2003.

"This optimism could translate into future earnings revisions," BofA wrote.