Who said,We may have disagreement, but
let some other country step on our tail
and see how quickly American unite.
It is a Western movie star.
Your quote is not quite accurate, and is also grammatically incorrect, but something very close to that is spoken by John Wayne in a poem he recites in the CD "America, Why I Love Her".
It is unclear whether he wrote the words.
See
http://www.amazon.com/America-Why-I-Love-Her/dp/B00005TQM2