In my experience, most "jews" don't even think about the subject. Or if they do, are totally conditioned by their culture, not from having actually objectively studied the subject even a little bit. Most do not agree strictly as a knee-jerk reaction. But an increasing number do, including Rabbis with whom I correspond, but who do not feel able to "go public" about it at this time. It's a matter of "culture" far more than history and theology.
>What's your take on who is celtic-related in europe?
I really go slow on trying to make specific associations because in my mind while it can be fascinating, it detracts from my main interest which is simply describing the association between The Lost Tribes of Israel and the Celts. Going from the Celts to specific countries is easy in a generic sense, but a source of unnecessary division and potential unhappiness on the other.
Worse, it can lead to a form of "Identity" theology, causing people to instead of concentrating on the word of God and what it means to them as a PERSON, want to identify with a GROUP. Dividing into groups is the first step towards dividing into YOU and ME, or US and THEM. I don't want any part of that.
It you carefully read the 3-MINUTE HISTORY at my Freeper LostTribe Profile below it will give you a solid grounding on basic Israelite history. Those historic facts, dates and definitions are the critical foundation of everything else. From there, you can confidently study the Celts and their expansion through Europe and America and see where they went. But be sure you have a BIG RED PENCIL to correct the many fundamental errors which you will find in copycat books on the market. Ha!
(A notable exception is Assyrian Tablets in the British Museum.)