Todavía no sé situar ese país en el mapa.

Todavía no means still not or not yet.

So:

• No sé situar ese país en el mapa = I don’t know how to locate that country on the map
• Todavía no sé situar ese país en el mapa = I still don’t know how to locate that country on the map / I don’t know how to locate that country on the map yet

It gives the idea that this may change later: maybe the speaker expects to learn it eventually.

In many contexts, todavía no and aún no mean the same thing.

Because saber + infinitive is a very common structure in Spanish for knowing how to do something.

So:

• Sé situar = I know how to locate / place
• No sé situar = I don’t know how to locate / place

This is different from simply using the verb situar by itself.

Compare:

• Sitúo ese país en el mapa = I place/locate that country on the map
• Sé situar ese país en el mapa = I know how to place/locate that country on the map

In this sentence, the point is not that the speaker is actively locating it right now, but that they lack the ability or knowledge to do so.

Here, situar means to locate, to place, or to identify where something is.

In this sentence, situar ese país en el mapa means something like:

• to locate that country on the map
• to place that country on the map
• to know where that country is on a map

In natural English, you might also say:

• I still can’t place that country on the map
• I still don’t know where that country is on the map

In Spain, situar sounds very natural in this kind of sentence.

Spanish has three common demonstratives:

• este = this (near the speaker)
• ese = that (near the listener or not especially near the speaker)
• aquel = that over there / that one farther away

So ese país means that country.

In practice:

• este país = this country
• ese país = that country
• aquel país = that country over there / that distant country

In many real conversations, ese is often the most neutral choice for that.

Because en el mapa is the normal Spanish expression for on the map when talking about location or identifying where something is.

So:

• situar algo en el mapa = to locate something on the map

Even though en often means in, it also has several uses that English expresses with on, depending on context.

Here, sobre el mapa would usually sound more physical, like something literally resting on top of a map. For geographic location, en el mapa is the natural choice.

Because Spanish often leaves out subject pronouns when the verb already makes the subject clear.

• sé already means I know
• so yo is not necessary

That is why:

• Todavía no sé situar ese país en el mapa is completely normal
• Yo todavía no sé situar ese país en el mapa is also possible, but it sounds more emphatic

You would add yo if you wanted contrast or emphasis, for example:

• Yo todavía no sé situar ese país en el mapa, pero ella sí.
  = I still don’t know how to locate that country on the map, but she does.

Sé has a written accent to distinguish it from se.

• sé = I know (from saber)
• se = a pronoun, as in se llama, se ve, etc.

So in your sentence:

• sé = I know

This accent is important because it changes the word’s function and meaning.

País has an accent because the stress falls on the second vowel: pa-ÍS.

The accent mark shows that a and í are pronounced in separate syllables:

• pa-ís = two syllables

Without the accent, Spanish spelling rules would suggest a different pronunciation. So the accent helps show the correct stress and syllable break.

Yes. In this sentence, aún no and todavía no both mean still not / not yet.

So these are both correct:

• Todavía no sé situar ese país en el mapa.
• Aún no sé situar ese país en el mapa.

For many learners, todavía is often easier to remember and more common in everyday use, but both are perfectly good here.

Yes, it is idiomatic and natural in Spain.

A Spaniard might also say:

• No sé ubicar ese país en el mapa
• No sé dónde está ese país
• No sabría situar ese país en el mapa

But situar ... en el mapa is a very normal and elegant way to express the idea.

A useful nuance:

• situar sounds a bit like identify/locate
• ubicar also means locate, though usage can vary by region
• saber dónde está is simpler and more direct: to know where it is

Yes. In natural English, that is often the best translation.

Literally, no sé situar is I don’t know how to locate/place. But in real usage, it often means:

• I can’t locate
• I can’t place
• I don’t know where to place

So:

• Todavía no sé situar ese país en el mapa
  can naturally be understood as
  I still can’t place that country on the map

This is a good example of how Spanish uses saber + infinitive where English may prefer can’t in normal translation.

The structure is:

Todavía no + sé + infinitive + noun phrase + prepositional phrase

More specifically:

• Todavía no = still not / not yet
• sé = I know
• situar = to locate / place
• ese país = that country
• en el mapa = on the map

So the sentence is built like this:

• Todavía no → time/negation idea
• sé situar → I know how to locate
• ese país → the thing being located
• en el mapa → where it is being located

That makes it a very useful model for other sentences, such as:

• Todavía no sé cocinar paella.
  = I still don’t know how to cook paella.
• Todavía no sé encontrar la calle.
  = I still don’t know how to find the street.