Cole no I don't think it's anything to do with British cultural imperialism, changing words of foreign origin etc. That's a different thing altogether.
Lucia, like Lucy, derives from Latin, and has been around as an alternative to Lucy for centuries in the UK, just a lot less popular than Lucy. It was pronounced 'loo-sha'. Hence the island name. In the same way we had Mary and Maria, Clare and Clara, Ann(e) and Anna.
At the same time, in Italy and Spain and other countries they also had the name 'Lucia' with a Latin origin, pronounced variously 'loo-chee-a', 'loo-see-a' 'loo-thee-a' etc. Lucia was a lot more popular in these countries, and of course they didn't use Lucy. In France they used Lucie (or Luce I believe).
Now Lucia is becoming popular over here, often with the Italian or Spanish pronunciation, but it is certainly not just an Italian or Spanish name.