There was a good More Or Less (uk radio programme) episode about this last week. Essentially, the European statistics on this tend to be based on excess mortality during hot periods, while US stats currently are much more about what words are used on death certificates. Very different measures and hard to compare.

There is. In Texas, if a field worker has a heart attack on a hot day it’ll be reported as a heart attack.

In France, the same exact situation would be reported as a heat casualty leading to heart attack.

US numbers in the popular twitter stat are officially recoded heat deaths whereas EU numbers are all excess deaths. Supposedly if you look at excess deaths the numbers for both places look the same.

IMO even that's not a proper comparison though because you cannot compare Alaska to Texas, or Rome to Helsinki and thus throwing all of these in together for discussing heat deaths us just pure nonsense and rage bait.