Do U.S. citizens who are residents of Puerto Rico pay U.S. federal income tax or other tax on income from other countries?

If a US citizen receives social security benefits they must pay income taxes on a portion of those benefits if they have another source of income which equals $25K if single or $32K if married. ALL other types of income are subject to US federal income taxes; including income from other countries.

They may, it depends on what taxes they paid in those countries and what country it is.

they pay US income tax

of course

yea