Use a PowerShell hash table/associative array to translate a country abbreviation to its full name.

CountryLoopup.ps1

$CountryLookup = [ordered]@{
    "AD"="ANDORRA"
    "AE"="UNITED ARAB EMIRATES"
    "AF"="AFGHANISTAN"
    "AG"="ANTIGUA AND BARBUDA"
    "AI"="ANGUILLA"
    "AL"="ALBANIA"
    "AM"="ARMENIA"
    "AO"="ANGOLA"
    "AQ"="ANTARCTICA"
    "AR"="ARGENTINA"
    "AS"="AMERICAN SAMOA"
    "AT"="AUSTRIA"
    "AU"="AUSTRALIA"
    "AW"="ARUBA"
    "AX"="ÅLAND ISLANDS"
    "AZ"="AZERBAIJAN"
    "BA"="BOSNIA AND HERZEGOVINA"
    "BB"="BARBADOS"
    "BD"="BANGLADESH"
    "BE"="BELGIUM"
    "BF"="BURKINA FASO"
    "BG"="BULGARIA"
    "BH"="BAHRAIN"
    "BI"="BURUNDI"
    "BJ"="BENIN"
    "BL"="SAINT BARTHÉLEMY"
    "BM"="BERMUDA"
    "BN"="BRUNEI DARUSSALAM"
    "BO"="BOLIVIA, PLURINATIONAL STATE OF"
    "BQ"="BONAIRE, SINT EUSTATIUS AND SABA"
    "BR"="BRAZIL"
    "BS"="BAHAMAS"
    "BT"="BHUTAN"
    "BV"="BOUVET ISLAND"
    "BW"="BOTSWANA"
    "BY"="BELARUS"
    "BZ"="BELIZE"
    "CA"="CANADA"
    "CC"="COCOS (KEELING) ISLANDS"
    "CD"="CONGO, THE DEMOCRATIC REPUBLIC OF THE"
    "CF"="CENTRAL AFRICAN REPUBLIC"
    "CG"="CONGO"
    "CH"="SWITZERLAND"
    "CI"="CÔTE D'IVOIRE"
    "CK"="COOK ISLANDS"
    "CL"="CHILE"
    "CM"="CAMEROON"
    "CN"="CHINA"
    "CO"="COLOMBIA"
    "CR"="COSTA RICA"
    "CU"="CUBA"
    "CV"="CAPE VERDE"
    "CW"="CURAÇAO"
    "CX"="CHRISTMAS ISLAND"
    "CY"="CYPRUS"
    "CZ"="CZECH REPUBLIC"
    "DE"="GERMANY"
    "DJ"="DJIBOUTI"
    "DK"="DENMARK"
    "DM"="DOMINICA"
    "DO"="DOMINICAN REPUBLIC"
    "DZ"="ALGERIA"
    "EC"="ECUADOR"
    "EE"="ESTONIA"
    "EG"="EGYPT"
    "EH"="WESTERN SAHARA"
    "ER"="ERITREA"
    "ES"="SPAIN"
    "ET"="ETHIOPIA"
    "FI"="FINLAND"
    "FJ"="FIJI"
    "FK"="FALKLAND ISLANDS (MALVINAS)"
    "FM"="MICRONESIA, FEDERATED STATES OF"
    "FO"="FAROE ISLANDS"
    "FR"="FRANCE"
    "GA"="GABON"
    "GB"="UNITED KINGDOM"
    "GD"="GRENADA"
    "GE"="GEORGIA"
    "GF"="FRENCH GUIANA"
    "GG"="GUERNSEY"
    "GH"="GHANA"
    "GI"="GIBRALTAR"
    "GL"="GREENLAND"
    "GM"="GAMBIA"
    "GN"="GUINEA"
    "GP"="GUADELOUPE"
    "GQ"="EQUATORIAL GUINEA"
    "GR"="GREECE"
    "GS"="SOUTH GEORGIA AND THE SOUTH SANDWICH ISLANDS"
    "GT"="GUATEMALA"
    "GU"="GUAM"
    "GW"="GUINEA-BISSAU"
    "GY"="GUYANA"
    "HK"="HONG KONG"
    "HM"="HEARD ISLAND AND MCDONALD ISLANDS"
    "HN"="HONDURAS"
    "HR"="CROATIA"
    "HT"="HAITI"
    "HU"="HUNGARY"
    "ID"="INDONESIA"
    "IE"="IRELAND"
    "IL"="ISRAEL"
    "IM"="ISLE OF MAN"
    "IN"="INDIA"
    "IO"="BRITISH INDIAN OCEAN TERRITORY"
    "IQ"="IRAQ"
    "IR"="IRAN, ISLAMIC REPUBLIC OF"
    "IS"="ICELAND"
    "IT"="ITALY"
    "JE"="JERSEY"
    "JM"="JAMAICA"
    "JO"="JORDAN"
    "JP"="JAPAN"
    "KE"="KENYA"
    "KG"="KYRGYZSTAN"
    "KH"="CAMBODIA"
    "KI"="KIRIBATI"
    "KM"="COMOROS"
    "KN"="SAINT KITTS AND NEVIS"
    "KP"="KOREA, DEMOCRATIC PEOPLE'S REPUBLIC OF"
    "KR"="KOREA, REPUBLIC OF"
    "KW"="KUWAIT"
    "KY"="CAYMAN ISLANDS"
    "KZ"="KAZAKHSTAN"
    "LA"="LAO PEOPLE'S DEMOCRATIC REPUBLIC"
    "LB"="LEBANON"
    "LC"="SAINT LUCIA"
    "LI"="LIECHTENSTEIN"
    "LK"="SRI LANKA"
    "LR"="LIBERIA"
    "LS"="LESOTHO"
    "LT"="LITHUANIA"
    "LU"="LUXEMBOURG"
    "LV"="LATVIA"
    "LY"="LIBYA"
    "MA"="MOROCCO"
    "MC"="MONACO"
    "MD"="MOLDOVA, REPUBLIC OF"
    "ME"="MONTENEGRO"
    "MF"="SAINT MARTIN (FRENCH PART)"
    "MG"="MADAGASCAR"
    "MH"="MARSHALL ISLANDS"
    "MK"="MACEDONIA, THE FORMER YUGOSLAV REPUBLIC OF"
    "ML"="MALI"
    "MM"="MYANMAR"
    "MN"="MONGOLIA"
    "MO"="MACAO"
    "MP"="NORTHERN MARIANA ISLANDS"
    "MQ"="MARTINIQUE"
    "MR"="MAURITANIA"
    "MS"="MONTSERRAT"
    "MT"="MALTA"
    "MU"="MAURITIUS"
    "MV"="MALDIVES"
    "MW"="MALAWI"
    "MX"="MEXICO"
    "MY"="MALAYSIA"
    "MZ"="MOZAMBIQUE"
    "NA"="NAMIBIA"
    "NC"="NEW CALEDONIA"
    "NE"="NIGER"
    "NF"="NORFOLK ISLAND"
    "NG"="NIGERIA"
    "NI"="NICARAGUA"
    "NL"="NETHERLANDS"
    "NO"="NORWAY"
    "NP"="NEPAL"
    "NR"="NAURU"
    "NU"="NIUE"
    "NZ"="NEW ZEALAND"
    "OM"="OMAN"
    "PA"="PANAMA"
    "PE"="PERU"
    "PF"="FRENCH POLYNESIA"
    "PG"="PAPUA NEW GUINEA"
    "PH"="PHILIPPINES"
    "PK"="PAKISTAN"
    "PL"="POLAND"
    "PM"="SAINT PIERRE AND MIQUELON"
    "PN"="PITCAIRN"
    "PR"="PUERTO RICO"
    "PS"="PALESTINE, STATE OF"
    "PT"="PORTUGAL"
    "PW"="PALAU"
    "PY"="PARAGUAY"
    "QA"="QATAR"
    "RE"="RÉUNION"
    "RO"="ROMANIA"
    "RS"="SERBIA"
    "RU"="RUSSIAN FEDERATION"
    "RW"="RWANDA"
    "SA"="SAUDI ARABIA"
    "SB"="SOLOMON ISLANDS"
    "SC"="SEYCHELLES"
    "SD"="SUDAN"
    "SE"="SWEDEN"
    "SG"="SINGAPORE"
    "SH"="SAINT HELENA, ASCENSION AND TRISTAN DA CUNHA"
    "SI"="SLOVENIA"
    "SJ"="SVALBARD AND JAN MAYEN"
    "SK"="SLOVAKIA"
    "SL"="SIERRA LEONE"
    "SM"="SAN MARINO"
    "SN"="SENEGAL"
    "SO"="SOMALIA"
    "SR"="SURINAME"
    "SS"="SOUTH SUDAN"
    "ST"="SAO TOME AND PRINCIPE"
    "SV"="EL SALVADOR"
    "SX"="SINT MAARTEN (DUTCH PART)"
    "SY"="SYRIAN ARAB REPUBLIC"
    "SZ"="SWAZILAND"
    "TC"="TURKS AND CAICOS ISLANDS"
    "TD"="CHAD"
    "TF"="FRENCH SOUTHERN TERRITORIES"
    "TG"="TOGO"
    "TH"="THAILAND"
    "TJ"="TAJIKISTAN"
    "TK"="TOKELAU"
    "TL"="TIMOR-LESTE"
    "TM"="TURKMENISTAN"
    "TN"="TUNISIA"
    "TO"="TONGA"
    "TR"="TURKEY"
    "TT"="TRINIDAD AND TOBAGO"
    "TV"="TUVALU"
    "TW"="TAIWAN, PROVINCE OF CHINA"
    "TZ"="TANZANIA, UNITED REPUBLIC OF"
    "UA"="UKRAINE"
    "UG"="UGANDA"
    "UM"="UNITED STATES MINOR OUTLYING ISLANDS"
    "US"="UNITED STATES"
    "UY"="URUGUAY"
    "UZ"="UZBEKISTAN"
    "VA"="HOLY SEE (VATICAN CITY STATE)"
    "VC"="SAINT VINCENT AND THE GRENADINES"
    "VE"="VENEZUELA, BOLIVARIAN REPUBLIC OF"
    "VG"="VIRGIN ISLANDS, BRITISH"
    "VI"="VIRGIN ISLANDS, U.S."
    "VN"="VIET NAM"
    "VU"="VANUATU"
    "WF"="WALLIS AND FUTUNA"
    "WS"="SAMOA"
    "YE"="YEMEN"
    "YT"="MAYOTTE"
    "ZA"="SOUTH AFRICA"
    "ZM"="ZAMBIA"
    "ZW"="ZIMBABWE"
}