[VadeRetro]

Menzies, an amateur historian, insists that the fleet never turned back, but instead rounded the Cape of Good Hope and then went on to discover the New World.

According to Menzies' view, the Chinese sent expeditions in North America as far inland as Kansas and, from San Francisco Bay, up the Sacramento River into Glenn County.

They left in 1421 and circled the globe, including visiting inland Kansas? However they got to Kansas--and back out to their ships--they weren't gone long enough.

[VadeRetro]

... they weren't gone long enough.

... Considering they were back in China by 1423.