@pk thank you for your answer. The W-9 form is not requested by my employer, but my bank. Apparently, this is the way they want me to communicate my SSN.
For 2020, I still believe that I should be considered as a nonresident alien with a tax residency in France, as I will not meet the Substantial Presence Test (my presence in the US during 2020 will count 117 days on 12/31/2020). If that is correct, I do not feel confortable with signing a W-9 form this year.
For 2021, I have to admit that I am even more confused. I understand from your reply that it will depend on whether or not the IRS considers me as a researcher. In fact, it has become quite common for Universities to employ researchers under H-1B visa. Incidentally, it is a big issue under COVID-19 related travel restrictions as most exceptions for academics only apply to J-1 holders. H-1Bs are too often presented to the public as Big Tech visas.
On the IRS website "Taxation of Alien Individuals by Immigration Status – H-1B" under Section II.E, one can read:
If the H-1B alien is treated for U.S. income tax purposes as a resident of a country with which the United States has an income tax treaty, he or she may benefit from a reduced rate of U.S. federal income tax on certain types of U.S. source income.
On the IRS website "Tax Treaty between the USA and France" under Article 20, one can read:
An individual who is a resident of a Contracting State immediately before his visit to the other Contracting State and who, at the invitation of the Government of that other State or of a university or other recognized educational or research institution situated in that other State, visits that other State for the primary purpose of teaching or engaging in research, or both, at a university or other recognized educational or research institution shall be taxable only in the first- mentioned State on his income from personal services for such teaching or research for a period not exceeding 2 years from the date of his arrival in the other State. An individual shall be entitled to the benefits of this paragraph only once.
I would be really curious about how one can contest the eligibility of academics under H-1B visa to this tax treaty benefits.
