@LightningBolt , Bom dia senor.
While you offer an inordinately complicated scenario, let us simplify first, before trying to solve and/or opine.
(a) You a citizen of Portugal, currently living in Switzerland on a resident visa.
(b) You are entering US on a J-1 visa and based on your passport issued by Portugal. That you were a resident of Switzerland just priorly is mostly not germane.
(b) While in the USA , and assuming that this is your first entry as a J-1 in the last six years, you would be treated as a Non-Resident ( NRA) for Two years and therefore taxed on your US sourced/connected income only.
(c) Because of your citizenship ( Portugal ), it is the tax treaty between Portugal and US that will be in effect.
I need to go back and refresh my memory ( all 85 years of it ) on US-Portugal Tax treaty in general and the treatment of students/trainees/Research scholars in particular ( esp. regarding treatment of foreign stipends while in the US ---- generally most "out of country " stipends are not taxable income to the J-1 visitor ). So I will be back.
In the meantime, if there are other pertinent factors to consider, please add to this thread.
Is there more I can do for you ?
Obrigdo, Senor
pk
