The average US musician knows the C/D/E, and possibly moveable Do/Re/Mi (where Do is the tonic of whatever major key you're singing in). The fixed Do system is

The average US musician knows the C/D/E, and possibly moveable Do/Re/Mi (where Do is the tonic of whatever major key you're singing in). The fixed Do system isn't even much covered in basic college-level music theory in the US (to my recollection); I doubt most performers will know much about it. About asking the Portuguese musician to learn 7 English words, and switch from fixed Do to the C/D/E system... well, the problem is not that it's hugely difficult, but that it will seem like a foolish choice to music teachers. Who would teach this new system? The benefits of the new system have to be huge and obvious if it's going to gain any ground, because the existing system is everywhere. Tell a teacher that "here's a new system! Only a miniscule fraction of extant sheet music is available for you and your students, you'll have to re-write all of your teaching materials, and you'll have to force your students to learn the American C/D/E system with English-language-only mneumonics!" It doesn't sound like a winning argument to me.