Why does Loewen consider the Mayflower overrated?

I believe the answer to your question is the fact that Loewen cites the Mayflower's landing at Plymouth as an accident, meaning that they've merely been blown off course on their way to Virginia. He also explains that possibly, they'd meant to miss Virginia and settle in New England on purpose. He goes onto say that there were only thirty-three pilgrims onboard a ship carrying 102 settlers. Regardless, Loewen states that the Pilgrims are falsely given credit as the founders os America, when in fact, Jamestown and Spanish settlements preceded them.