There have been Copages/Coppages in America since the middle of the seventeenth century and the number of Americans bearing this surname is now far higher than in the UK.
In the US, the Coppage-Coppedge Family Association, formed in 1948, now has several hundred members throughout North America. The association traces the origins of the surname to Edward and William Coppage who migrated from England to America between 1648 and 1652 where they settled in Virginia. Over the years, the association has organised annual family reunions in various locations in the Eastern USA and has helped to distribute the Coppage-Coppedge Family Chronicles. This book was first published in 1955; the third edition is currently under preparation.
The Coppage-Coppedge Family Association can be found online at ccfa.website

Bronze marker in Virginia commemorating Edward Coppedge
The extent to which the surname is more common in America than in Britain can be seen by a comparison of search results on Ancestry.com for the twentieth century.

The Copage name is most commonly found in California while Coppage and Coppedge occur most frequently in Texas, North Carolina, Virginia and Kentucky.
Perhaps the most famous American Copage is Marc Copage born in 1962 and who as a child actor starred in the sitcom Julia for all three seasons beginning in 1968.

One possibility is that Marc is descended from a slave who took the surname of his owner.