I think El Salvador is the best Bitcoin adoption country right now. They have a small population but already have a policy to apply legal payments with Bitcoin. In the long run, people will choose Bitcoin as a regular means of payment. This will increase Bitcoin adoption rate.
Although the US has many ATMs, Bitcoin is still not considered a legal means of payment like the dollar and Bitcoin users still make up a small percentage of the entire population.
Yes. US may have the bigger population when it comes to crypto users but never has the government adopt bitcoin as a legal tender and still majority are the dollar earners and users. For me, El Salvador even takes the lead in global bitcoin adoption. Although this nation has a lesser population compared to US but its own president has the first initiative to propose a bill making bitcoin as a legal tender. And now, when other countries saw that it was a success even though there were some circumstances that had took place on its first months, start to see bitcoin too which has potentials to be a good currency that will bring progress to the country's economy.
El Salvador is also a country that creates an effect for other countries that have policies with cryptocurrencies. Laos and Russia accept Bitcoin mining as legal hop activity. Ukraine is the second country to consider Bitcoin as a legal means of payment. Those things are great.