The number of ATMs doesn't matter, what matters is the usage, and for that, we don't have any numbers.
For example, a few years ago a tobacco shop network in France started selling Bitcoins, it had 5200 shops, which would have put them at that point over double the numbers of US ATMs.
This aside, the US can't take the lead as despite every single piece of news about China, Japan, Nigeria, Venezuela, or Malta or god knows what country was labeled as Bitcoin's new capital the US has always been in the lead when it comes to real-life usage and to the numbers of bitcoin owners. You can see that everything from ATMs, nodes, LN nodes, shops, companies, investment funds, jobs in cryptocurrencies, everything is concentrated in the US, China dominated for a while with the hashrate and the fake volume exchanges okchina and huobi did, now it is left with zero.
Poeple might not like it but the US is a clear leader right now, and Salvador won't change a thing, a country with 1/40 of the GDP of California doens't matter n a global scale.
This is very true. Even if US is not like El Salvador (wherein, they are the first country to accept bitcoin as legal tender), still their market is small as compared to US.
However, the move of El Salvador is also important as it may change the perception of many users across the globe.
That it is possible for the government to accept bitcoin as legal tender along with their local fiat money.
It can drive other users to more adoption as they change their perspectives towards crypto usage.
Many, I believe, will be inspired to take a look at bitcoin because of their government's initiative.
But of course, we can't deny the fact that US is leading the pack. The 2020 statistics shows they have the highest btc trading volume according to statista.
Now, would be interesting to see by next year if El Salvador will be included in this graphical representation.
https://www.statista.com/statistics/1195753/bitcoin-trading-selected-countries/