Well, their leader IS red, white, and blue. 
However, Transformers admittedly does have its 
roots traditionally in Macross and other anime 
that came out in the 80's...

But I still like to think of giant alien robots 
that turn into cars and stuff as homegrown 
American to a degree.

Here's Silverbolt, from Transformers, air 
commander of the Aerialbots getsalt team. 

-Chaotic Serenity