As a reminder, the forward P/E is the current stock price divided by analysts' estimates of earnings per share in 12 months. 

Source yardeni.com - Refinitiv
US goes it alone:
Far to the top, valued at 19.9, the historically better-valued U.S. index has had a much higher forward P/E than its Eurozone runner-up for several years now. Future earnings are currently valued at about one-third higher in the US than in Europe.
 
The USA, less sensitive to market declines:
Where the U.S. index stands out is not only in its higher valuation but especially in its resistance to market declines. In 2016, the forecasted P/Es of the indices were concentrated, but from 2017 onwards, the gap between the USA and the others widened, thanks to the rise of technology stocks. The observation is the same since 2020, when all the indices lose quite strongly in value (from 18.0 to 14.0 for the Euro zone, 16.0 to 12.0 for the United Kingdom) while the US index stagnates and falls much less violently (from 23.0 to 21.0). It took a recent collapse in US technology stocks to see the US forward P/E fall sharply below 20.0 (19.9 as of January 27).
 
Are emerging markets being sold off?
The MSCI Emerging Markets Index has a forward P/E of 12.2, its future earnings are 40% less valued than those of the US. The recent difficulties of Chinese real estate giant China Evergrande and the general discounting of Chinese stocks seem to have weighed on confidence in the future performance of emerging markets (China accounts for ⅓ of the MSCI emerging markets index).