Harry would have to be out of Dumbledore's reach at Salem (unlikely, given the extent of Dumbledore's influence and meddling).

The second note states that magical America can protect Harry from Dumbledore. If Harry isn't outside Dumbledore's reach at Salem, and Dumbledore knows this when writing the note, then he is lying.

Dumbledore would have to let Harry keep the cloak before sending him to Salem. (fairly likely, but not guaranteed).

Technically speaking, Dumbledore can't take the Cloak from Harry by force, since its powers apparently rely on formal and deliberate transfer of ownership. I suppose he could resort to blackmail, but doing that before sending Harry to America would almost certainly result in complete breaking of ties (at least friendly ties).

Dumbledore would have to be alive (also fairly likely, although if this follows canon then Dumbledore will die at some point)

Given everything else that happens (with Hermione's death as the strongest example), I think we can be fairly certain that this story will not follow canon plot developments except by coincidence.