Which type of insurer is considered alien in the U.S.?

An alien insurer is defined as one that is domiciled outside of the United States. This means that the company is incorporated and primarily operates under the regulations of a foreign country. The classification of an insurer as alien is important in the context of insurance regulation and market participation in the U.S. insurance industry, as it influences how the company is licensed, the regulations it must adhere to, and its ability to operate within various states in the U.S.

In this scenario, the other options do not fit the criteria for an alien insurer. An insurer with headquarters in the U.S. is considered domestic, while an insurer based in one U.S. state is classified as a local or domestic insurer as well. An insurer that operates in multiple U.S. states can also be classified as a national or regional insurer, but it does not fall into the "alien" category unless it is based outside the country. Therefore, the correct identification of an alien insurer as one domiciled outside the United States accurately reflects its designation within insurance terminology.