Always check both local currency and USD returns when evaluating international markets.
1. You exchange Dollars for Euros
2. You buy a stock in Euros
3. You hold the stock in Euros for a period of time
4. You sell the stock in Euros
5. You exchange your Euros for Dollars.
The difference in the exchange rate in step 1 and 5 can have a very large impact on your total return, often times a larger impact than step 3.
But the euro itself has climbed ~10% YTD vs the dollar (≈ $1.02 → $1.12-1.18). So you get an ~18% gain if you invest in MSCI Europe in dollars.
Europe hasn't "beaten" US stocks because its companies suddenly out-executed; most of the gap is the stronger euro.
Not that it matters who’s "winning." My gripe is with US headlines that shout "Japan stocks are on fire" or "Europe stocks are on fire," when what’s really happening is that global markets are rising together and currency swings make one region look better than another.