Symbolism, Imagery, Allegory
Dracula ain't just about the paranoia that your neighbor might be a psycho. It's about the (hopefully more justified—we hope your neighbors are the kind you can borrow a cup of sugar from) paranoia that the British Empire was going the way of the dodo bird.
At the time Bram Stoker was writing Dracula (1897), Great Britain's world-wide empire was starting to crumble. Other countries, such as Germany and the US, were starting to gain power both economically and politically. A lot of British people were worried that Britain would lose its status as the greatest world power. (Spoiler: it did.)
That's why some literary critics, like Stephen Arata, have argued that Dracula's move to Britain reflects British people's worry that foreigners (especially from the east) would invade Britain. If Britain really was becoming weaker, as people feared, maybe foreigners—even people from countries that Britain had formerly colonized—would come and take over.
For more on this interpretation of Dracula, check out Stephen Arata's awesome article, "The Occidental Tourist: Dracula and the Anxiety of Reverse Colonization" (there's a link to it in our "Best of the Web" section).