Is this remote worldwide or in the US only? The job ad says "employees on several continents and more than a dozen countries" which implies it's world-wide, but

Is this remote worldwide or in the US only? The job ad says "employees on several continents and more than a dozen countries" which implies it's world-wide, but when I apply it says "I understand that upon employment, proof of legal right to work in the US and completion of an I-9 form will be required".