I like the concept. The plot line seems intriguing. A little confused on how swapping earth from another era is going to save humanity.

A minor point is that Jamestown in Virginia was founded 1607. While the Mayflower didn't arrive until 1653 or so. The chapel in Jamestown, as it existed in that century, was built decades before the Mayflower arrived in Massachusetts.

I must confess that this is mere persnicketiness on my part. Just that I've been to the Jamestown Fort several times now and know the basic history of Jamestown pretty well. So you're probably safe ignoring me.

Overall, I think you've got something interesting in your work.