I don't think that it will surprise anybody that has crypto knowledge that El Salvador, still remains the top country when you are talking about Bitcoin adoption on a national level afterall they don't have any competitors yet at the national level. Let them continue to enjoy the lone top spot until another country seizes the opportunity of hodling the store of value as a national asset and have their citizens spend it like their fiat then maybe we can see a comparison. Bitcoin adoption is driven by individuals, groups and institutions and it is doing very fine as it is but I guess that the adoption will increase faster if more countries will act like El Salvador.

Because El Salvador is the top crypto-friendly country and accepts Bitcoin as legal tender. So usually Google will recognise it as the number one Bitcoin-friendly country. Their Bitcoin adaptation is quite strong, legal tender means it would be used like their fiat currency. So till now, El Salvador is at the top as a Bitcoin supporter. Even the government is holding Bitcoin. I hope we will see more countries like El Salvador in the in the near future. 

Bitcoin is no longer a legal tender in the Central African Republic. The law was repelled by the parliament after a few months. Bitcoin is a legal tender only in El Salvador. There was a genuine reason for this law but it might be connected to poor planning, infrastructural deficit and of course external influence.
https://www.centralbanking.com/central-banks/currency/digital-currencies/7956294/car-to-drop-crypto-as-legal-tender

https://www.jbgsmining.com/en/post/central-african-republic-drops-bitcoin-as-legal-tender

With the acceptance of Bitcoin as their legal tender, no doubt why it is the top result when someone searches for a "bitcoin country". To be honest, when they didn't accepted it yet as a legal tender there are other countries that were considered one before. Like Malta, Japan, other Asian countries too. But because of this action that El Salvador did, they were the first in the history that has become an actual country that has adopted it.

Not to mention the other countries that became first crypto friendly countries. Central African Republic supposed to be the next one but they didn't continue it from happening. But soon, we will see some other countries that might also declare Bitcoin as their legal tender. It is only a matter of time but we should be happy that the number of countries that recognizes Bitcoin is increasing. Maybe sometime in the next months, there will be countries like UAE that will be more friendly to crypto because of the type of government and rules that they are setting.

This nation was hot years ago in a previous market cycle by making Bitcoin legal tender. It is a first ever nation makes it in Bitcoin history and so far it is the only nation applies it practically.

On coinmarketcap, there are two nations, one is El Salvador and another one is Central African Republic but only El Salvador is practically doing this.

https://coinmarketcap.com/legal-tender-countries/

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They put it in accordance with the facts, El Salvador was the first country to make bitcoin legal tender, people in that country are definitely finding out about what bitcoin is and inviting people outside the country to make searches for "bitcoin" & its relationship to " El Salvador". From the title of your thread, are we talking about the future here? i'm not sure El Salvador will still be the top searcher for the "bitcoin" keyword in the next 3 years.

Good to know that and honestly speaking, it should remain on the top.
Few years back, I didn't even knew El Salvador existed, my be my geography is weak but there was nothing about the country to remember it for.
But that has changed and El Salvador became the first country to accept bitcoin as a legal tender and the rest is history.
As bitcoin achieves more organic growth, I hope other countries will follow El Salvador's steps and accept bitcoin as a legal tender.

Its simply based on Google Trend results, which is calculated by checking in which country people searched for keywod "Bitcoin" the most, relative to all other searches. And in that ranking El Salvador is first, Nigeria 2nd, Switzerland usually 3rd (depending on the timeframe you set.

For example, this is the top 5 in the last 12 months

Central African Republic decided to repel the law that made Bitcoin legal tender due to different reasons but external influence was a major factor. If you have read my post after the one you quoted, I mentioned factors like poor planning and infrastructural deficit let me also add a high rate of illiteracy. The IMF criticized the policy but the main attack came from the Bank of Central African States (BEAC). This regional apex bank controls the financial system of Cameroon, the Central African Republic, Chad, the Republic of Congo, Gabon and Equatorial Guinea. 

Immediately CAR made Bitcoin a legal tender BEAC issued a statement declaring the CAR’s adoption of the new cryptocurrency law “null and void” and in violation of the tenets of the regional bloc. It was reported that the country had to bow to the pressure of the regional central bank until they came up with a policy on cryptocurrency. A country that doesn't have full control over its financial policy will not be able to make independent decisions.