This debate has been had ad naseum inside and outide the serious country counting community. Most of us who've been to "every country" subscribe to the 193 UN members + 2-5 others. Why others? Most commonly accepted is Vatican City - who could join the UN but chooses not to. Everyone agrees. Next most agreed upon is Kosovo, who's recognized by way over half the UN member states, but due to Russia/Serbia vetos is unable to join. So that gets you 195. Lots of people also add Palestine, which is also recognized by over half the UN - but that's a discussion I think we should avoid. So, that's the 196 I use. Lots of others add Taiwan as 197. however, it has extremely limited UN recognition.

So...pick a list. Your list. TCC, Guinness, UN. MTP, NomadMania....there's no right or wrong answer...but I guarantee once you "hit them all" you'll look for a list of autonomous places to go after so that you still have something to chase...