近い将来　米国へ入国する短期旅行者に対してもVISAのような物が必要になるそうです。 プレスリリース Starting next year sometime, visitors from Visa Waiver Countries (VWC) heading to the United States will need a pre-travel authorization. The Electronic System for Travel Authorization (ESTA) will be required prior to boarding a U.S.-bound airplane or cruise ship. The requirement will go into effect next year Press Release