There’s no real proof for any European discovery of America before Columbus. There MAY have been — most likely yes the Vikings, Irish etc. could have found parts of N Am, but the only one for which we have definite proof and who had the lasting historical impression and who set up contacts was Signor Columbus
Yours in Christ,
Monsignor McBedford
But in 1960, undeniable proof of Vikings in North America came to light at LAnse aux Meadows in Newfoundland, Canada. Several Norse Viking pieces and clear Icelandic- style house foundations gave proof positive that Vikings had indeed landed, and briefly settled, in North America 500 years before Columbus.
More recent archaeological work has revealed over 300 years of sporadic contact between the Greenlandic Norse and various Indian, Inuit, and other Native American peoples, concentrated primarily in the Canadian Arctic. (http://www.mnh.si.edu/vikings/1137.html)