correlation between parts of a sentence

[Klpno]

Hello everyone

I'd like to ask about the grammar structure of a sentence in the following passage:

The United Nations has struggled for decades to distinguish and characterize who or what an international labour migrant is. It proposed that a migrant worker be defined as a person who enters a country other than that of which he/she is a citizen for at least 12 months, after having been absent for one year or longer.

I have difficulty understanding the second sentence:

... a person who enters a country other than that of which he/she is a citizen for at least 12 months.

Does "for at least 12 months" refer to the stay in the country the person enters. For example, a person who is a citizen of Russia enters the USA and he/she has been in the US for 12 months.

And I cannot figure out which "after having been absent for one year or longer" refer to and where the person has been absent.

[Diverhank]

Your understanding of the second sentence is correct. He enters (or re-enters) the US and stays for at least 12 months. The last sentence refers to the USA (as in your example) and the "one year or longer" refers to the person had been away from the US at least a year before re-entering the US (and stays for at least 12 months).

[Klpno]

Thank you very much, diverhank.