Nominal GDP is ridiculously stupid. It treats the entire GDP as being a part of the international exchange market which is completely brain dead. The international exchange value of your next haircut is completely meaningless. Further, the US economy will probably grow faster than China's this year solely because US inflation is 6% whereas China's CPI is only 1.3%. If a country's currency exchange rate drops overnight by 10% the economy "shrinks" by 10% even if it literally produced all the exact same things as it did yesterday.
I wish journalists would stop using nominal GDP and just admit that China is already the world's largest economy and everyone else would stop obsessing over nominal GDP too. But I guess that won't happen.