I found an answer to this question on Quora:
"No - AliExpress is just one of the marketplaces that is available using Oberlo.
There is also Oberlo Supply marketplace - a data base of carefully selected and verified suppliers that are based in Europe, North America and China.
All in all, using Oberlo you’re free to import products from either AliExpress, or Oberlo Supply marketplace."
However, I cannot find a way to access the Oberlo Supply marketplace. The Oberlo app on my store only shows Ali Express products.
Can anyone help me access the Oberlo Supply marketplace?