It wasn't proposed as a commemoration, but rather as a thanksgiving to god for the mecies shown to the union. I don't know how it was received in the South, but it has been taken over by New England historical myth.
In that version, the "Pilgrim Fathers" who landed at Plymouth Rock in 1620 gave thanks to their boy god for surviving the first year. There is absolutely no historical record for such an event, but the boys in New England have been successful in hijaking the holiday. I'm certain it is observed in the South now.
In fact, the first English colony in North America was at Roanoke Island in 1584. However, when the ship sailed back to England in 1585, they were involved in the panic over the Armada, and were not allowed to leave England. It was not until after 1590 that they were able to sail back to Roanoke Island, and the colonists, along with Virginia Dare, the first English child born in North America, had all disappeared. I won't go into details, but it seems they went to the mainland, and were absorbed into an Indian tribe.
The next English settlement was at Jamestown in 1607. Other small settlements were made on Massachusetts Bay, too, before the so-called Pilgrim Fathers showed up in 1620. But the New England historical myth has become so pervasive, that many Americans believe all that bullshit. The symoblism of the modern thanksgiving celebration is turkeys, "Pilgrims" dress in 17th century garb and pumpkins, squash and indian corn. It's pointless, of course, to rail against the inaccuracy. The New England boys have succeded in making their story paramount.