could any of the kingdoms at middle earth attack the southern continents?

[Belegorn]

Originally Posted by tom the eldest

The numenorians probably have,either when they are exploring,or trying to find aman.

The Númenóreans knew where Aman was, but they were forbidden to sail there. They could sail west but not so far as to lose sight of the land of Númenor. They could, however, see Avallónë which is a city on Tol Eressëa "easternmost of the Undying Lands." [Sil., Akallabêth, p. 324] All I know is that they did sail:

"ever eastward and not westward, from the darkness of the North to the heats of the South, and beyond the South to the Nether Darkness; and they came even into the inner seas, and sailed about Middle-earth"