環境

$ aws --version
=> aws-cli/2.2.7 Python/3.8.8 Darwin/18.7.0 exe/x86_64 prompt/off

原因

regionがus-east-1じゃなかったから

NG:

$ aws route53domains list-domains                                                                                                                                                                               
=> Could not connect to the endpoint URL: "https://route53domains.ap-northeast-1.amazonaws.com/"

OK:

$ aws route53domains list-domains --region us-east-1
=> {
    "Domains": [
        {
            "DomainName": "example1.com",
            "AutoRenew": true,
            "TransferLock": false,
            "Expiry": "2021-06-01T09:53:28+09:00"
        },
        {
            "DomainName": "example2.jp",
            "AutoRenew": true,
            "TransferLock": true,
            "Expiry": "2022-06017T00:00:00+09:00"
        },
    ]
}

詳細

ドメインを取得する際の**regionはus-east-1が固定**らしい。。。
公式のExamplesに小さく書いてたが、この注釈の書き方はあまりにも分かりにくい。。。。

To list the domains that are registered with the current AWS account
The following list-domains command lists summary information about the domains that are registered with the current AWS account.
This command runs only in the us-east-1 Region. If your default region is set to us-east-1, you can omit the region parameter.