Here is a JSON object which contains a list of all countries and their associated abbreviations. Thought others might find this useful.

JSONCountries.json

[
	{"US":"United States"},
	{"CA":"Canada"},
	{"AF":"Afghanistan"},
	{"AL":"Albania"},
	{"DZ":"Algeria"},
	{"DS":"American Samoa"},
	{"AD":"Andorra"},
	{"AO":"Angola"},
	{"AI":"Anguilla"},
	{"AQ":"Antarctica"},
	{"AG":"Antigua and/or Barbuda"},
	{"AR":"Argentina"},
	{"AM":"Armenia"},
	{"AW":"Aruba"},
	{"AU":"Australia"},
	{"AT":"Austria"},
	{"AZ":"Azerbaijan"},
	{"BS":"Bahamas"},
	{"BH":"Bahrain"},
	{"BD":"Bangladesh"},
	{"BB":"Barbados"},
	{"BY":"Belarus"},
	{"BE":"Belgium"},
	{"BZ":"Belize"},
	{"BJ":"Benin"},
	{"BM":"Bermuda"},
	{"BT":"Bhutan"},
	{"BO":"Bolivia"},
	{"BA":"Bosnia and Herzegovina"},
	{"BW":"Botswana"},
	{"BV":"Bouvet Island"},
	{"BR":"Brazil"},
	{"IO":"British lndian Ocean Territory"},
	{"BN":"Brunei Darussalam"},
	{"BG":"Bulgaria"},
	{"BF":"Burkina Faso"},
	{"BI":"Burundi"},
	{"KH":"Cambodia"},
	{"CM":"Cameroon"},
	{"CV":"Cape Verde"},
	{"KY":"Cayman Islands"},
	{"CF":"Central African Republic"},
	{"TD":"Chad"},
	{"CL":"Chile"},
	{"CN":"China"},
	{"CX":"Christmas Island"},
	{"CC":"Cocos (Keeling) Islands"},
	{"CO":"Colombia"},
	{"KM":"Comoros"},
	{"CG":"Congo"},
	{"CK":"Cook Islands"},
	{"CR":"Costa Rica"},
	{"HR":"Croatia (Hrvatska)"},
	{"CU":"Cuba"},
	{"CY":"Cyprus"},
	{"CZ":"Czech Republic"},
	{"DK":"Denmark"},
	{"DJ":"Djibouti"},
	{"DM":"Dominica"},
	{"DO":"Dominican Republic"},
	{"TP":"East Timor"},
	{"EC":"Ecudaor"},
	{"EG":"Egypt"},
	{"SV":"El Salvador"},
	{"GQ":"Equatorial Guinea"},
	{"ER":"Eritrea"},
	{"EE":"Estonia"},
	{"ET":"Ethiopia"},
	{"FK":"Falkland Islands (Malvinas)"},
	{"FO":"Faroe Islands"},
	{"FJ":"Fiji"},
	{"FI":"Finland"},
	{"FR":"France"},
	{"FX":"France, Metropolitan"},
	{"GF":"French Guiana"},
	{"PF":"French Polynesia"},
	{"TF":"French Southern Territories"},
	{"GA":"Gabon"},
	{"GM":"Gambia"},
	{"GE":"Georgia"},
	{"DE":"Germany"},
	{"GH":"Ghana"},
	{"GI":"Gibraltar"},
	{"GR":"Greece"},
	{"GL":"Greenland"},
	{"GD":"Grenada"},
	{"GP":"Guadeloupe"},
	{"GU":"Guam"},
	{"GT":"Guatemala"},
	{"GN":"Guinea"},
	{"GW":"Guinea-Bissau"},
	{"GY":"Guyana"},
	{"HT":"Haiti"},
	{"HM":"Heard and Mc Donald Islands"},
	{"HN":"Honduras"},
	{"HK":"Hong Kong"},
	{"HU":"Hungary"},
	{"IS":"Iceland"},
	{"IN":"India"},
	{"ID":"Indonesia"},
	{"IR":"Iran (Islamic Republic of)"},
	{"IQ":"Iraq"},
	{"IE":"Ireland"},
	{"IL":"Israel"},
	{"IT":"Italy"},
	{"CI":"Ivory Coast"},
	{"JM":"Jamaica"},
	{"JP":"Japan"},
	{"JO":"Jordan"},
	{"KZ":"Kazakhstan"},
	{"KE":"Kenya"},
	{"KI":"Kiribati"},
	{"KP":"Korea, Democratic People's Republic of"},
	{"KR":"Korea, Republic of"},
	{"KW":"Kuwait"},
	{"KG":"Kyrgyzstan"},
	{"LA":"Lao People's Democratic Republic"},
	{"LV":"Latvia"},
	{"LB":"Lebanon"},
	{"LS":"Lesotho"},
	{"LR":"Liberia"},
	{"LY":"Libyan Arab Jamahiriya"},
	{"LI":"Liechtenstein"},
	{"LT":"Lithuania"},
	{"LU":"Luxembourg"},
	{"MO":"Macau"},
	{"MK":"Macedonia"},
	{"MG":"Madagascar"},
	{"MW":"Malawi"},
	{"MY":"Malaysia"},
	{"MV":"Maldives"},
	{"ML":"Mali"},
	{"MT":"Malta"},
	{"MH":"Marshall Islands"},
	{"MQ":"Martinique"},
	{"MR":"Mauritania"},
	{"MU":"Mauritius"},
	{"TY":"Mayotte"},
	{"MX":"Mexico"},
	{"FM":"Micronesia, Federated States of"},
	{"MD":"Moldova, Republic of"},
	{"MC":"Monaco"},
	{"MN":"Mongolia"},
	{"MS":"Montserrat"},
	{"MA":"Morocco"},
	{"MZ":"Mozambique"},
	{"MM":"Myanmar"},
	{"NA":"Namibia"},
	{"NR":"Nauru"},
	{"NP":"Nepal"},
	{"NL":"Netherlands"},
	{"AN":"Netherlands Antilles"},
	{"NC":"New Caledonia"},
	{"NZ":"New Zealand"},
	{"NI":"Nicaragua"},
	{"NE":"Niger"},
	{"NG":"Nigeria"},
	{"NU":"Niue"},
	{"NF":"Norfork Island"},
	{"MP":"Northern Mariana Islands"},
	{"NO":"Norway"},
	{"OM":"Oman"},
	{"PK":"Pakistan"},
	{"PW":"Palau"},
	{"PA":"Panama"},
	{"PG":"Papua New Guinea"},
	{"PY":"Paraguay"},
	{"PE":"Peru"},
	{"PH":"Philippines"},
	{"PN":"Pitcairn"},
	{"PL":"Poland"},
	{"PT":"Portugal"},
	{"PR":"Puerto Rico"},
	{"QA":"Qatar"},
	{"RE":"Reunion"},
	{"RO":"Romania"},
	{"RU":"Russian Federation"},
	{"RW":"Rwanda"},
	{"KN":"Saint Kitts and Nevis"},
	{"LC":"Saint Lucia"},
	{"VC":"Saint Vincent and the Grenadines"},
	{"WS":"Samoa"},
	{"SM":"San Marino"},
	{"ST":"Sao Tome and Principe"},
	{"SA":"Saudi Arabia"},
	{"SN":"Senegal"},
	{"SC":"Seychelles"},
	{"SL":"Sierra Leone"},
	{"SG":"Singapore"},
	{"SK":"Slovakia"},
	{"SI":"Slovenia"},
	{"SB":"Solomon Islands"},
	{"SO":"Somalia"},
	{"ZA":"South Africa"},
	{"GS":"South Georgia South Sandwich Islands"},
	{"ES":"Spain"},
	{"LK":"Sri Lanka"},
	{"SH":"St. Helena"},
	{"PM":"St. Pierre and Miquelon"},
	{"SD":"Sudan"},
	{"SR":"Suriname"},
	{"SJ":"Svalbarn and Jan Mayen Islands"},
	{"SZ":"Swaziland"},
	{"SE":"Sweden"},
	{"CH":"Switzerland"},
	{"SY":"Syrian Arab Republic"},
	{"TW":"Taiwan"},
	{"TJ":"Tajikistan"},
	{"TZ":"Tanzania, United Republic of"},
	{"TH":"Thailand"},
	{"TG":"Togo"},
	{"TK":"Tokelau"},
	{"TO":"Tonga"},
	{"TT":"Trinidad and Tobago"},
	{"TN":"Tunisia"},
	{"TR":"Turkey"},
	{"TM":"Turkmenistan"},
	{"TC":"Turks and Caicos Islands"},
	{"TV":"Tuvalu"},
	{"UG":"Uganda"},
	{"UA":"Ukraine"},
	{"AE":"United Arab Emirates"},
	{"GB":"United Kingdom"},
	{"UM":"United States minor outlying islands"},
	{"UY":"Uruguay"},
	{"UZ":"Uzbekistan"},
	{"VU":"Vanuatu"},
	{"VA":"Vatican City State"},
	{"VE":"Venezuela"},
	{"VN":"Vietnam"},
	{"VG":"Virigan Islands (British)"},
	{"VI":"Virgin Islands (U.S.)"},
	{"WF":"Wallis and Futuna Islands"},
	{"EH":"Western Sahara"},
	{"YE":"Yemen"},
	{"YU":"Yugoslavia"},
	{"ZR":"Zaire"},
	{"ZM":"Zambia"},
	{"ZW":"Zimbabwe"}
]

You have a typo on VG: "Virigan" should be "Virgin".

{"SS" : "South Sudan"} is now a country

Thank you !

Thank u very much u saved my time ^^

This is not a full list. Serbia is missing.
This list (bottom one) is apparently more complete: https://gist.github.com/Keeguon/2310008

Also Montenegro is missing.