If the u. s. should have never been in iraq, according to some people, then why did the England, Poland, and Australia all invade as well?

I've seen some videos about why we invaded iraq and that we never should have because they didn't have WMD's and all that, like the government lied about, as usual, but, then if that's true, why did England, POLAND, and Australia, invade as well?

If the u. s. should have never been in iraq, according to some people, then why did the England, Poland, and Australia all invade as well?
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