This is a small island outside the United States, which is
🇺🇸 the same as the American flag. Including the nine island territories of the United States defined by the International Organization for Standardization, namely Wake Island, Midway Island, Johnston Atoll, Howland Island, Baker Island, Kingman Reef, Palmyra Atoll, and Navarre Sand island. On some platforms, the system is displayed as UM.
🇺🇲 is the Emoji of a country/region‘s flag, and its meaning is flag: U.S. Outlying Islands. The Emoji 🇺🇲 is composed of two regional indicator letters, namely 🇺 and 🇲. The country/region's 2-letter code for U.S. Outlying Islands is UM, so the letters corresponding to the two region indicator letters are U and M. 🇺🇲 is displayed as a whole flag on most platforms and as a two-letter symbol on a few platforms.