As Jno points out, Leif Ericson got there 500 years before Columbus.
Columbus sought funding from any available source in his quest to find a western route to the Orient. He started with Portugal, then tried his native Italy (or, more accurately, the Venetian court). He also asked for financial support, through his brother, from England. Henry VIII eventually agreed to finance the project but his support came too late because Columbus had already found backing from Spain.
So, if Columbus had failed on his original mission (but safely returned home) he might have tried again under the English flag. (Actually, of course, Columbus failed anyway, since he never found a western route to the Orient).
If Columbus's ship had sunk (or he couldn't obtain further funding elsewhere) any future quest would have required the funding from one of the major European courts, such as those of Venice, Rome, Portugal or England.
Chis