Europe and Asia are separated by mountains. Geographically that's at least as valid as splitting America on a canal, and splitting Africa from Asia on a canal. If anything the mountains are a more significant barrier to travel and migration than those canals

If we were to rearrange the continents if anything we should split up Asia further, and split Africa into Northern Africa and Sub-Saharan Africa (maybe giving Sub-Saharan Africa to the same new continent as the Arabian peninsula, but that's debatable)