The following countries use E26 bulbs

Anguilla, Aruba, Bahamas, Barbados, Belize, Bermuda, Canada, Cayman Islands, Colombia, Costa Rica, Cuba, Dominican Republic, Ecuador, El Salvador, Guatemala, Haiti, Honduras, Jamaica, Japan, Libya, Mexico, Nicaragua, Panama, Taiwan, Trinidad and Tobago, United States, Venezuela and British Virgin Islands.

The following countries use E27 bulbs

Afghanistan, Aland Islands, Albania, Algeria, Andorra, Angola, Antigua and Barbuda, Argentina, Armenia, Australia, Austria, Azerbaijan, Bahrain, Bangladesh, Belarus, Belgium, Benin, Bhutan, Bolivia, Bosnia And Herzegovina, Botswana, Bouvet Island, Brazil, British Indian Ocean Territory, Brunei, Bulgaria, Burkina Faso, Burma, Burundi, Cambodia, Cameroon, Cape Verde, Central African Republic, Chad, Chile, China, Christmas Island, Cocos (Keeling) Islands, Comoros, Congo, The Democratic Republic Of The Congo, Cook Islands, Côte d'Ivoire, Croatia, Cyprus, Czech Republic, Denmark, Djibouti, Dominica, Egypt, Equatorial Guinea, Eritrea, Estonia, Ethiopia, Falkland Islands (Malvinas), Faroe Islands, Fiji, Finland, France, French Guiana, French Polynesia, French Southern Territories, Gabon, Gambia, Georgia, Germany, Ghana, Gibraltar, Greece, Greenland, Grenada, Guadeloupe, Guernsey, Guinea, Guinea Bissau, Guyana, Heard Island And Mcdonald Islands, Holy See (Vatican City State), Hong Kong, Hungary, Iceland, India, Indonesia, Islamic Republic Of Iran, Iraq, Ireland, Isle Of Man, Israel, Italy, Jersey, Jordan, Kazakhstan, Kenya, Kiribati, Korea, Kosovo, Kuwait, Kyrgyzstan, Lao People's Democratic Republic, Latvia, Lebanon, Lesotho, Liberia, Liechtenstein, Lithuania, Luxembourg, Macao, Macedonia, The Republic Of, Madagascar, Malawi, Malaysia, Maldives, Mali, Malta, Martinique, Mauritania, Mauritius, Mayotte, Republic of Moldova, Monaco, Mongolia, Montenegro, Montserrat, Morocco, Mozambique, Myanmar, Namibia, Nauru, Nepal, Netherlands, Netherlands Antilles, New Caledonia, New Zealand, Niger, Nigeria, Niue, Norfolk Island, Norway, Oman, Pakistan, Palestinian Territory, Occupied, Papua New Guinea, Paraguay, Peru, Philippines, Pitcairn, Poland, Portugal, Qatar, Reunion, Romania, Russia, Rwanda, Saint Barthélemy, Saint Helena, Saint Kitts And Nevis, Saint Lucia, Saint Martin, Saint Pierre And Miquelon, Samoa, San Marino, Sao Tome And Principe, Saudi Arabia, Senegal, Serbia, Seychelles, Sierra Leone, Singapore, Slovakia, Slovenia, Solomon Islands, Somalia, South Africa, South Georgia And The South Sandwich Islands, South Korea, Spain, Sri Lanka, St. Vincent, Sudan, Suriname, Svalbard And Jan Mayen, Swaziland, Sweden, Switzerland, Syria, Tajikistan, (United Republic Of) Tanzania, Thailand, Timor Leste, Togo, Tokelau, Tonga, Tunisia, Turkey, Turkmenistan, Turks And Caicos Islands, Tuvalu, Uganda, Ukraine, United Arab Emirates, United Kingdom, Uruguay, Uzbekistan, Vanuatu, Vietnam, Wallis And Futuna, Western Sahara, Yemen, Zambia, Zimbabwe