The article itself says that is hasn't been concluded who built the mound. You've already conceded Middle East links to the region by admitting the X is found in the ancient Americas, which is already confirmed by bioarcheology. The X came from N, which came from West Asia, largely found around present-day Turkey and throughout the region. One of the Odin's ancestors came from the area of modern-day Turkey, and the X has been found in similarities to groups both in Sweden and ancient America, while the Adena mound sites have been found to be similar to those found in Sweden. The high-level of X found along the Atlantic-Artic travel routes suggest it could have came to the continent that way, but that is for archeologists to determine. See: 
"Who built the ancient stone architecture of Canada and New England," Richard Thornton. August 22, 2010.