"<span>The British hoped to tighten control over the empire" would be the best option, but the main reason beyond this was that they wanted to discourage trade with other nations, in order to increase profits. </span>
The geographical feature that separates the United Kingdom from the rest of Europe is the North Sea.
The North Sea is the water body that lies between the United Kingdom and the continental part of Europe. With France and Benelux being just on the south of it, and the Scandinavian Peninsula on the east. We can also include the English Channel, as it is separating part of the north of France and the south of the United Kingdom.
This was not always the case, and the territory of the United Kingdom was relatively recently (geologically speaking) connected by land with the rest of Europe through a land that is now bellow water called Doggerland, and that was until the end of the last ice age.
Because the American government saw them as Japanese people over in japan who wanted to destroy America. They put them in camps so they could contain them before they could start any destruction, which was not true.