For some background on Pre-Columbian contacts across the Bering Strait, you might want to check out this answer from u/TheAlaskan, as well as this answer by u/reedstilt.

I will add that since those answers have been written, there has been new archeological evidence of trade across the Bering Strait in the form of Venetian glass beads found in Alaska that predate 1492.

This question can be answered by another question: Who was supposed to discover America from Kamchatka? Russian explorers wouldn’t reach the easternmost end of Siberia until the 17th century, long after Columbus, and neither the Chinese, Japanese, or even earlier the Mongols ventured that far north. Of course the native peoples of that area such as the Chuchki engaged in some trade and contact with the peoples across the Bering Straight, but it can be supposed that to these indigenous peoples the American continent was always a known entity in the same way that we don’t claim that the Inuit discovered America.