Answer is clear and concise. Left a particular case where the subject has been living abroad for less than a certain number of days a year. Let's say a subject moved out to a foreign country in June for example. He had 6 months of US income and by the end of the year will have the last 6 months of foreign income. I am not sure but the rules above might not apply.
The answers above are good enough (at least for myself) and the particular case is of less importance but better for completeness for people seeking information

Thanks again Stephanie. Maybe someone has filed US taxes with a mixed US&foreign income in same year