Looking at the US elections, I was surprised to see that in a dozen or more states, the vote count is less than a million. USA is still a big, fairly empty country. Most of the people living in those big empty states vote republican, as do the majority of rural populations living in states whose urban populations vote Democrat. Maybe they think that their needs are being ignored by the Democrats, or perhaps it is more complicated, or not a rational thing at all. Here in Israel, Jews who live "on the periphery" also tend to give their votes to right wing parties.
A friend in the village, born in Pennsylvania, said he would be voting for the first time in years, and it's actually at least 30 years since he spent any amount of time in the US. Since PA is a battleground state, he thought it was important enough to make the effort this time.
UK citizens (like me) lose the right to vote after being away for 15 years, last time I checked. But 15 years seems reasonable enough. Israeli citizens can't vote when they are abroad, unless they are members of diplomatic missions, of course.