You are entering from "another country" if you are coming from the Moon.
For this purpose "country" has to be interpret as stepping on any land outside of the US.
For this purpose "country" has to be interpret as stepping on any land outside of the US.
"Land" is legally (and generally) defined as pertaining to planet earth. In this case the crew did not step on any land outside of the US. The moon does not have land.
Interesting. Where have you read this? Intuitively, it seems very weird for a lawmaker to specify the planet the law would apply to.