Why do Christians keep converting to things like Wicca and Paganism?

You answered your question yourself. "I am and always have been a pantheistic pagan." What's more to say?

What you're talking about is ignorant people being judgmental of you, possibly even racist by assuming that because you were born into a Jewish family, you must, therefore, be Jewish in faith. There is no way to "legally" convert, since religion is not sanctioned or controlled by the government (despite indications and certain groups petitioning for the contrary). Pantheistic pagans don't really have the same kind of initiatory structure that Wicca and some other forms of modern neo-paganism have (as you mentioned), but many people who come to paganism decide to do a self-dedication ceremony of some type.

This is something that may be meaningful to you or not and you could do one if you like. That is an entirely personal choice and a very personal ceremony and will likely have little or no meaning to these people who consider you Jewish out of ignorance. Don't do things spiritually or religiously just to please others... that's the whole reason you "left" your native faith, isn't it?

You say you have been pagan since you could remember, so what would be the point of such a ceremony to you on a personal level? What difference does it really make if people who have no stake in your spiritual life make the silly assumption that you're Jewish? Why does it matter?

You cannot, and you never will, change the way other people think. Even if could make some grand public gesture of conversion, there would still be stubborn souls who think "once a Jew, always a Jew." Nothing you can do about them and they have no investment in your religious life anyhow, so why bother?

Just be you, be authentic, ignore or correct those people who make ignorant assumptions about you and go on being who you are, unconcerned with what others think of your path. -Scarlet.

There is no legal or official conversion that comes with some kind of paperwork or proof. There is no legal recognition for any religion. Basically the law has to accept that you are what you say you are.

I know Jews are very strict about people converting to Judaism, there is a process to do so and a large community that will recognize the completion of that process. However, this is simply not the case with Pantheism and you are not going to find the same kind of structure and ritual... and nothing about it is going to be recognized by everyone around you. For your own personal rite of passage, you can always devise some kind of meaningful ceremony.

I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.