Just as an observation I think the flag that is shown is the country where you connected last. So it is possible that what you ask (country at account creation) is not stored. I have also noticed for multiple players that country flag changes (as they move around), and even myself I appeared with at least 3 flags.
I have some scrapers for data (see
https://zero-k.info/Forum/Thread/34840?postID=248087), so based on that I can give you a list of countries that the scraper did not see (it will depend on the moment of the scraping, which is not done regularly, and where the players connect from). I did not check carefully the analysis (maybe a different flag code is used for some countries), but seems consistent with what I remember.
The list :
[Spoiler]
Name,Code
American Samoa,AS
Angola,AO
Anguilla,AI
Antarctica,AQ
Benin,BJ
"Bonaire, Sint Eustatius and Saba",BQ
Bouvet Island,BV
British Indian Ocean Territory,IO
Burkina Faso,BF
Burundi,BI
Cabo Verde,CV
Central African Republic,CF
Chad,TD
Christmas Island,CX
Cocos (Keeling) Islands,CC
Comoros,KM
Congo,CG
"Congo, The Democratic Republic of the",CD
Cook Islands,CK
Côte d'Ivoire,CI
Dominica,DM
Equatorial Guinea,GQ
Eritrea,ER
Eswatini,SZ
Falkland Islands (Malvinas),FK
French Southern Territories,TF
Gabon,GA
Gambia,GM
Greenland,GL
Grenada,GD
Guinea,GN
Guinea-Bissau,GW
Haiti,HT
Heard Island and McDonald Islands,HM
Holy See (Vatican City State),VA
Kiribati,KI
"Korea, Democratic People's Republic of",KP
Lesotho,LS
Malawi,MW
Marshall Islands,MH
Mauritania,MR
Mayotte,YT
"Micronesia, Federated States of",FM
Montserrat,MS
Nauru,NR
Niger,NE
Niue,NU
Norfolk Island,NF
Palau,PW
Pitcairn,PN
Rwanda,RW
Saint Barthélemy,BL
"Saint Helena, Ascension and Tristan da Cunha",SH
Saint Martin (French part),MF
Saint Pierre and Miquelon,PM
Sao Tome and Principe,ST
Senegal,SN
Sierra Leone,SL
Solomon Islands,SB
South Georgia and the South Sandwich Islands,GS
South Sudan,SS
Sudan,SD
Svalbard and Jan Mayen,SJ
"Taiwan, Province of China",TW
"Tanzania, United Republic of",TZ
Timor-Leste,TL
Togo,TG
Tokelau,TK
Tonga,TO
Turkmenistan,TM
Turks and Caicos Islands,TC
Tuvalu,TV
United States Minor Outlying Islands,UM
Vanuatu,VU
"Virgin Islands, British",VG
"Virgin Islands, U.S.",VI
Wallis and Futuna,WF
Western Sahara,EH
Edit: and just because I was curious, the total numbers and per capita values below. Do note that this is for a period of 15 years of something, so not only active accounts.
[Spoiler]| country_code | users | population | users_per_capita | name |
| FI | 1201 | 5617310 | 213.8 | Finland |
| EE | 257 | 1360546 | 188.89 | Estonia |
| NZ | 936 | 5213944 | 179.52 | New Zealand |
| AU | 4558 | 26713205 | 170.63 | Australia |
| SE | 1789 | 10606999 | 168.66 | Sweden |
| DK | 886 | 5977412 | 148.22 | Denmark |
| DE | 12453 | 84552242 | 147.28 | Germany |
| CA | 5704 | 39742430 | 143.52 | Canada |
| LT | 404 | 2859110 | 141.3 | Lithuania |
| LV | 261 | 1871871 | 139.43 | Latvia |
| IS | 54 | 393396 | 137.27 | Iceland |
| NL | 2465 | 18228742 | 135.23 | Netherlands |
| NO | 718 | 5576660 | 128.75 | Norway |
| US | 43030 | 345426571 | 124.57 | United States |
| CZ | 1269 | 10735859 | 118.2 | Czechia |
| GB | 8074 | 69138192 | 116.78 | United Kingdom |
| CH | 975 | 8921981 | 109.28 | Switzerland |
| AT | 968 | 9120813 | 106.13 | Austria |
| MT | 57 | 539607 | 105.63 | Malta |
| PL | 3718 | 38539201 | 96.47 | Poland |
| LU | 64 | 673036 | 95.09 | Luxembourg |
| BE | 1061 | 11738763 | 90.38 | Belgium |
| HU | 844 | 9676135 | 87.22 | Hungary |
| FR | 5542 | 66548530 | 83.28 | France |
| SI | 164 | 2118697 | 77.41 | Slovenia |
| IE | 388 | 5255017 | 73.83 | Ireland |
| HR | 259 | 3875325 | 66.83 | Croatia |
| RU | 8826 | 144820423 | 60.94 | Russian Federation |
| SM | 2 | 33581 | 59.56 | San Marino |
| SK | 293 | 5506760 | 53.21 | Slovakia |
| SG | 306 | 5832387 | 52.47 | Singapore |
| LI | 2 | 39870 | 50.16 | Liechtenstein |
| BY | 444 | 9056696 | 49.02 | Belarus |
| UA | 1828 | 37860221 | 48.28 | Ukraine |
| SC | 6 | 130418 | 46.01 | Seychelles |
| PT | 453 | 10425292 | 43.45 | Portugal |
| CY | 52 | 1358282 | 38.28 | Cyprus |
| RO | 685 | 19015088 | 36.02 | Romania |
| RS | 235 | 6736216 | 34.89 | Serbia |
| BN | 16 | 462721 | 34.58 | Brunei Darussalam |
| ES | 1363 | 47910526 | 28.45 | Spain |
| BG | 183 | 6757689 | 27.08 | Bulgaria |
| GE | 103 | 3807670 | 27.05 | Georgia |
| IL | 251 | 9387021 | 26.74 | Israel |
| MC | 1 | 38631 | 25.89 | Monaco |
| ME | 15 | 638479 | 23.49 | Montenegro |
| IT | 1287 | 59342867 | 21.69 | Italy |
| KN | 1 | 46843 | 21.35 | Saint Kitts and Nevis |
| MD | 64 | 3034961 | 21.09 | "Moldova Republic of" |
| GY | 17 | 831087 | 20.46 | Guyana |
| GR | 204 | 10047817 | 20.3 | Greece |
| BH | 31 | 1607049 | 19.29 | Bahrain |
| BA | 54 | 3164253 | 17.07 | Bosnia and Herzegovina |
| UY | 55 | 3386588 | 16.24 | Uruguay |
| CL | 288 | 19764771 | 14.57 | Chile |
| KZ | 277 | 20592571 | 13.45 | Kazakhstan |
| MY | 440 | 35557673 | 12.37 | Malaysia |
| AD | 1 | 81938 | 12.2 | Andorra |
| AR | 519 | 45696159 | 11.36 | Argentina |
| AG | 1 | 93772 | 10.66 | Antigua and Barbuda |
| BB | 3 | 282467 | 10.62 | Barbados |
| MK | 19 | 1823009 | 10.42 | North Macedonia |
| TT | 15 | 1507782 | 9.95 | Trinidad and Tobago |
| VC | 1 | 100616 | 9.94 | Saint Vincent and the Grenadines |
| AM | 29 | 2973840 | 9.75 | Armenia |
| KW | 48 | 4934507 | 9.73 | Kuwait |
| ZA | 620 | 64007187 | 9.69 | South Africa |
| TH | 676 | 71668011 | 9.43 | Thailand |
| AE | 101 | 11027129 | 9.16 | United Arab Emirates |
| CR | 41 | 5129910 | 7.99 | Costa Rica |
| BR | 1688 | 211998573 | 7.96 | Brazil |
| BS | 3 | 401283 | 7.48 | Bahamas |
| PH | 845 | 115843670 | 7.29 | Philippines |
| BZ | 3 | 417072 | 7.19 | Belize |
| PA | 32 | 4515577 | 7.09 | Panama |
| LB | 41 | 5805962 | 7.06 | Lebanon |
| TR | 571 | 87473805 | 6.53 | Türkiye |
| KR | 325 | 51717590 | 6.28 | "Korea Republic of" |
| QA | 19 | 3048423 | 6.23 | Qatar |
| AL | 16 | 2791765 | 5.73 | Albania |
| MV | 3 | 527799 | 5.68 | Maldives |
| LC | 1 | 179744 | 5.56 | Saint Lucia |
| MU | 7 | 1271169 | 5.51 | Mauritius |
| FJ | 5 | 928784 | 5.38 | Fiji |
| WS | 1 | 218019 | 4.59 | Samoa |
| JM | 13 | 2839175 | 4.58 | Jamaica |
| PE | 147 | 34217848 | 4.3 | Peru |
| AZ | 41 | 10336577 | 3.97 | Azerbaijan |
| KG | 26 | 7186009 | 3.62 | Kyrgyzstan |
| JP | 443 | 123753041 | 3.58 | Japan |
| JO | 40 | 11552876 | 3.46 | Jordan |
| SA | 116 | 33962757 | 3.42 | Saudi Arabia |
| MN | 11 | 3475540 | 3.16 | Mongolia |
| PY | 20 | 6929153 | 2.89 | Paraguay |
| VE | 77 | 28405543 | 2.71 | "Venezuela Bolivarian Republic of" |
| MX | 316 | 130861007 | 2.41 | Mexico |
| NI | 16 | 6916140 | 2.31 | Nicaragua |
| TN | 27 | 12277109 | 2.2 | Tunisia |
| PS | 11 | 5495443 | 2.0 | "Palestine State of" |
| CO | 104 | 52886363 | 1.97 | Colombia |
| OM | 9 | 5281538 | 1.7 | Oman |
| LK | 37 | 23103565 | 1.6 | Sri Lanka |
| SV | 10 | 6338193 | 1.58 | El Salvador |
| SR | 1 | 634431 | 1.58 | Suriname |
| BO | 19 | 12413315 | 1.53 | "Bolivia Plurinational State of" |
| VN | 147 | 100987686 | 1.46 | Viet Nam |
| IQ | 59 | 46042015 | 1.28 | Iraq |
| BT | 1 | 791524 | 1.26 | Bhutan |
| EC | 22 | 18135478 | 1.21 | Ecuador |
| IR | 111 | 91567738 | 1.21 | "Iran Islamic Republic of" |
| UZ | 43 | 36361859 | 1.18 | Uzbekistan |
| ID | 331 | 283487931 | 1.17 | Indonesia |
| MA | 42 | 38081173 | 1.1 | Morocco |
| EG | 124 | 116538258 | 1.06 | Egypt |
| KH | 17 | 17638801 | 0.96 | Cambodia |
| DZ | 43 | 46814308 | 0.92 | Algeria |
| DO | 10 | 11427557 | 0.88 | Dominican Republic |
| DJ | 1 | 1168722 | 0.86 | Djibouti |
| HN | 9 | 10825703 | 0.83 | Honduras |
| GT | 15 | 18406359 | 0.81 | Guatemala |
| LY | 6 | 7381023 | 0.81 | Libya |
| MM | 42 | 54500091 | 0.77 | Myanmar |
| CU | 7 | 10979783 | 0.64 | Cuba |
| CN | 767 | 1419321278 | 0.54 | China |
| BW | 1 | 2521139 | 0.4 | Botswana |
| NP | 10 | 29651054 | 0.34 | Nepal |
| SY | 8 | 24672760 | 0.32 | Syrian Arab Republic |
| PK | 59 | 251269164 | 0.23 | Pakistan |
| LR | 1 | 5612817 | 0.18 | Liberia |
| IN | 228 | 1450935791 | 0.16 | India |
| KE | 8 | 56432944 | 0.14 | Kenya |
| LA | 1 | 7769819 | 0.13 | Lao People's Democratic Republic |
| YE | 5 | 40583164 | 0.12 | Yemen |
| AF | 5 | 42647492 | 0.12 | Afghanistan |
| PG | 1 | 10576502 | 0.09 | Papua New Guinea |
| TJ | 1 | 10590927 | 0.09 | Tajikistan |
| BD | 13 | 173562364 | 0.07 | Bangladesh |
| ZW | 1 | 16634373 | 0.06 | Zimbabwe |
| SO | 1 | 19009151 | 0.05 | Somalia |
| ZM | 1 | 21314956 | 0.05 | Zambia |
| ML | 1 | 24478595 | 0.04 | Mali |
| UG | 2 | 50015092 | 0.04 | Uganda |
| CM | 1 | 29123744 | 0.03 | Cameroon |
| MG | 1 | 31964956 | 0.03 | Madagascar |
| GH | 1 | 34427414 | 0.03 | Ghana |
| MZ | 1 | 34631766 | 0.03 | Mozambique |
| ET | 2 | 132059767 | 0.02 | Ethiopia |
| NG | 1 | 232679478 | 0.0 | Nigeria |
And for the people that like visuals: