(Firstly, can I just say that this is a really nice little puzzle and it is a shame it has never garnered the attention it deserves!) As for the solution, I believe your AI created this art to represent your travels using:
Minimalist representations of countries’ FLAGS.
To start with, we know from the text that you have visited 12 countries. Note then that the line of the artwork which represents the ‘key’ consists of 12 numbers separated by dashes: 5-5-8-5-8-17-7-7-11-7-11-11. We also know from the hints that:
Trinidad and Tobago was definitely one of the countries visited. Note that ‘Trinidad and Tobago’ is 17 letters long. Since the number 17 appears in the 12-number ‘key’, it would perhaps not be unreasonable to deduce that these numbers represent the lengths of the names of the 12 countries you visited.
So how might this country be represented in the image? Well, notice next that:
If you rotate the image by ninety degrees clockwise you can see a resemblance to a flag on a pole. So perhaps this might be a clue to focus on the flags of the 12 countries you visited.
Returning to the country mentioned in the hint:
The flag of Trinidad and Tobago is a thick black diagonal stripe on a red background (with two very thin white lines dividing the main colours). In a minimalist form, this could be represented by two backslashes: "\ \", indicating the divisions between the red and black sections.
There is one occurrence of the double-backslash in the image, in the second row of symbols. For the minimalist flag approach to work, this must be the part of the image representing Trinidad & Tobago.
So what could the other countries be, and how are they represented in the image? Well, here is one possible way to account for the 11 countries which do not throw the error:
(Numbers in brackets indicate the length of the country name.)
- Horizontal dashes can be interpreted as separations between horizontal stripes of colour (in Paraguay, Syria, South Africa, Honduras and Chile), and vertical bar symbols likewise for vertical bands of colour (in Algeria and Chile).
- The circle in the Paraguay flag represents the circular central emblem; the plus sign in the Swiss flag represents the Swiss cross.
- The open bracket in the Algeria flag represents the crescent moon. Asterisks represent stars (the ‘5*’ in Honduras being a shorthand for five stars).
- The solitary saltire cross represents a nation’s flag separated into 4 triangular blocks of colour along the diagonals.
- The two backslashes one above the other can represent the ‘double triangle’ shape of Nepal’s irregular flag.
Obviously there are some potential clashes here:
- The lone star could represent Vietnam, Somalia or Morocco (all 7 letters).
- The solitary saltire cross could represent Jamaica or Burundi (again, both 7 letters).
However, as a result of the order specified in the 'key', I have chosen countries which:
Fit with a pattern of always travelling in an easterly direction to the same or an earlier time zone (passing around the world only once), which could feasibly be a travel itinerary.
This way our key corresponds to: SYRIA (5) – NEPAL (5) – HONDURAS (8) – CHILE (5) – PARAGUAY (8) – TRINIDAD & TOBAGO (17) – MOROCCO (7) – ALGERIA (7) – SWITZERLAND (11) – BURUNDI (7) – SOUTH AFRICA (11) – and one final 11-letter country which throws the error code…
What could the final error-throwing country be? How about:
SAUDI ARABIA - since the country’s flag comprises only white Arabic writing (the Islamic creed, or shahada) above a horizontal sword on a green background and would prove difficult to translate into the ASCII figures required for this artwork. The string of numbers that makes up the 'flagpole' (1-4-5-3-8-15-4-7-7-6-9) could well be something like the lengths of the words in a rough translation of the writing. The fact it makes up the horizontal-lying flagpole could be as a result of the AI attempting to combine this translation with the depiction of the long sword.
Following a comment from @MOehm I revisited the precise countries I had identified to try and:
Use flags of countries whereby the 'flagpole' represented letters taken from particular positions within the other countries' names to create the name of the 12th problematic one (still Saudi Arabia, by the above ASCII-incompatible reasoning).
This produces the following alternative arrangement:
if we can assume that an eleven-letter alternative spelling of 'Guinea-Bissau' has been used in the puzzle...
And the twelfth country can then be derived as follows:
Key (length of country names): 5-5-8-5-8-17-7-7-11-7-11-11
'Flagpole' letter positions of the first 11: 1-4-5-3-8-15-4-7-7-6-9
7/11 guinea-Bissau (if an alternative spelling is used, e.g. using 'Bisau')
which spells out SAUDI ARABIA as before, but as a result of the AI finding an alternative way to represent the difficult-to-convert image of the flag. I find this a much more satisfactory solution, especially since it explains the chevrons using the flag of Bahrain - the only surplus symbols in the image are now those that make up the pole and flag edging.