TAIPEI—Taiwan has asked its office in Washington to remind the United States not to cause “unnecessary speculation or misunderstanding” after the White House deleted a social media post on COVID-19 vaccine donations that included Taiwan’s flag. A spokesman for the White House National Security Council called the use of the flag “an honest mistake” by the team handling graphics and social media that should not be viewed as a shift in U.S. policy towards Taipei, under which Washington does not formally recognize Taiwan’s government. The White House COVID-19 Response Team this week posted on Twitter an image giving details of U.S. vaccine donations globally, including last month’s Moderna shots sent to Taiwan. It showed the island’s flag along with those of others getting vaccines. Taiwan President Tsai Ing-wen re-tweeted it, adding: “Thank you to the U.S. for your generosity. Together, we will beat this pandemic.” However, the post was then …