The Ford Ka and Fiat 500 are built on the same platform that as developed by Fiat. Currently there are plans for Fiat to build the 500 at one of Chrysler’s North American plants, when the vehicle eventually goes on sale here. Chrysler also wants a small car that would share the same underpinnings as the 500 and Ka. Since US car buyers historically like larger cars, the only way to make a profit would be to some how manage to sell more of them and bringing the Ford Ka here could help achieve that goal. By building three cars all built on the same platform in the US, costs could be more evenly spread out. This would provide more fuel for the business case to bring the little Ka here since the vehicle could actually be profitable.
There is no word yet on if Ford does indeed plan on bringing the Ka here. If the Ka did come here, it would be one of the smallest vehicles on the road, since its only marginally bigger than the Smart ForTwo.