I'm not sure I understand your point. Just because the country is large doesn't necessarily mean that you need larger fire trucks?

(Or that America needs a one size fits all approach to fire trucks - things that work well in cities may not work well in rural areas)

Since you have typically much larger distances to travel, people want larger cars. You couldn't take american cars down some of those english roads.

What does the size of the country have to do with the size of firetrucks?