What I mean is, in what practical way could the EU ban ARM/Nvidia from their market, considering these manufacturers' chips are in many devices? Would that mean devices with those components would also be banned?

What I'm trying to get at is, with a sufficiently large merger, the emerging company may produce products so ubiquitous that it would be impractical to bar them from your economy, due to the widespread use of their products and their integration into other products.