There are plenty of examples of the word 'discover' being used to describe finding out things someone else already knows. eg the cops discovering who a murderer is, or the legal process of 'discovery' etc etc.

It isn't wrong to describe Europeans discovering America as long as you aren't claiming they were the first to discover it.

As a previously commentator mentioned, "colonized" is a much more fitting word than "discovery." The deeper problem, I think, with "discovery" is that it obscures the violence of the European settlement process -- the meta-genocides of the North American peoples and the transatlantic Slave Trade.

The discovery of America by Europeans is not the same as the colonization and settlement, although the discovery led to colonization. They are not synonyms.