This is an interesting debate. Many people say she is the best woman for the job and her being an American who worked for the Big tech is only one added advantage, bringing that knowledge along.
On the other side, this could be a sovereignty and reciprocity issue. A European would never be nominated for an equivalent job in the US. So I find it fair to discuss, but maybe this is a discussion that should have happened before. If there’s no legal restriction to hire a non-European, there’s no basis to attack this nomination in particular.
In any case I praise Vestager for not being afraid of breaking this tabu.