Any country in Europe, to start with (especially central and eastern Europe). But since living in 'Eretz Yisra'el is a mitzvah that can now be fulfilled in part ("in part" thanks to the Israeli government kicking Jews off land that allegedly belongs to "indigenous pipples") and since living in the Exile is nothing but a punishment for sins and always ends in tragedy, who wants to rebuild Jewish Poland (or Lithuania or Ukraine or Transylvania or any other such place)?
I don't know if you live in Poland or the United States, but if the former you should realize that the United States has never really been a part of "chr*stendom" as you understand it. It was settled by Protestant Biblical Fundamentalists to whom the world of the Bible was much more important than the post-Biblical chr*stian world. That is why American Fundamentalists have the nostalgia for restored Israel that European chr*stians feel for a restored medieval Holy Roman Empire, and they tend to (alone in the chr*stian world) even support the rebuilding of the Temple and the reinstitution of sacrifices (which European chr*stians would probably define as "the reign of antichrist"). That's what the chr*stian church gets for cutting off the Biblical canon so early!
Unfortunately, this puts American Fundamentalists in a sort of theological "no man's land," neither Jewish nor traditionally chr*stian, and they are despised and distrusted by both sides. If they knew more about chr*stian history and theology they would probably (as I have done) give up chr*stianity altogether for Noachism (G-d's covenant with non-Jewish mankind according to Judaism), but they cannot pry their minds away from the only worldview they have ever known, unnatural and mixed up as it is.
As a Noachide myself I don't believe in permanently reestablishing Jewish communities in the exile but in the complete ingathering of all Jews to 'Eretz Yisra'el, the rebuilding of the Temple, and the rule of Mashiach HaMelekh (King Messiah) and the Kingdom of G-d on earth.
I hope that by explaining my perspective you can understand my otherwise harsh words about eastern Europe.
Again, my apologies for being unfeeling and hurtful to you.