“[I]f they were the indigenous Jews of Palestine who got expand, there would be some Jews around the world today who have a genetic link connecting them to Palestine…”
There is NO SUCH THING as a ‘genetic link’ connecting anybody to ‘Palestine.’
DNA establishes genetic links between persons and other persons.
Not between persons & places.
All Jews worldwide do indeed have genetic links to all other Jews, regardless of where they or their ancestors have sojourned over the centuries since their expulsion — by ARABS (not ‘Romans’) — from the Land of Israel.