401(k) participant (U.S. citizen) died earlier this year – surviving spouse is Canandian citizen (she is a non-resident alien) was the sole beneficiary

surviving spouse would like to move the assets into an inherited 401(k) followed by an IRA transfer

Questions
Is she (as a Canadian citizen) eligible to transfer assets into an IRA (either under her own name or inherited IRA)?
Assuming yes, is it tax free transfer? like it would be for a U.S. citizen?

She is also concerned about taxation (both U.S. and Canada) upon taking distributions. My understanding taxation is dependent on the U.S./Canadian tax treaty – I am hoping someone can expand on the treaty – providing specifics

All guidance is appreciated

Thank you!