Shouldn't it be America is a big city? But that doesn't make sense though..
For some reason my first reply vanished the moment I hit the post button, so here it goes again:
No, because in Arabic the adjectives come after the noun. مَدينة أَمْريكِيّة كَبيرة madiinh amrikiyyh kabiirh -- city american big
Meaning a city that's american and big, thus a big American city.