Do people understand that Protestant christianity is very different from Catholic christianity?

As a fellow Protestant I must say that you are a little off track here. The first universal (or catholic) shurch developed into the Catholic faith which was the world church (with a division between the Eastern and the Western churches) until the time of the Feformation. Yes indeed there is a difference, however it can be honestly state theat the first churches did indeed develope into the Catholic church and theat the protestant faiths did not arrive until much later.