I think it is hard for people in smaller countries to grasp the diversity and the geographic expanse of all 50 states. In order for a candidate to actually, physically, travel to and meet with the population of voters, it takes TIME (and money) and all that time of them stumping on the election trail, the media follows them around looking for something to report. You can't compare elections in the US to an election in the UK. It's a completely different kind of problem to educate and reach and motivate the voters from Hawaii to Maine and Alaska to Florida.