I believe the Florida ones actually have an orange in the background. Illinois is a bluish white with a picture of Abe Lincoln in the back, along with a silhouette of the Chicago skyline and the state capitol building.
Yeah making plates look fancy does seem to be a mostly American thing. I suppose it's a result of state pride. Though there are some boring ones. Michigan and Ohio come to mind. But I suppose even those are more visually interesting than euro plates. And then you got vanity plates, which usually refers to having a particular combo of characters for the number, but there are also different plates you can get. For example my mom's plates are white with our state bird, the cardinal, on the left.
http://www.plateshack.com/y2k/Illinois/ily2k.html
Hope you had a good time in the colonies :P