Everyone that has made that "gotcha" argument has failed to say how they're different.
You do not practice what you preach since you failed to prove what you asserted about there being only one KJV. You challenge others to prove what they stated while you do not prove what you stated. Perhaps you were blindly repeating what you heard or read from a KJV-only source so that you have not checked the facts for yourself.
Perhaps your eyes are closed to seeing how they are different.
Another thread has been started in answer to your unproven claim, and it will provide details. It pointed out the fact that whole words not found in the 1611 edition were added in later editions. There are so many actual differences that they all cannot be listed in one post. You could see the evidence yourself by comparing the original 1611 edition of the KJV with a present post-1900 edition.
Here is one example that would show that the 1611 edition of the KJV was not given by inspiration of God.
At 2 Kings 24:19, the 1611 edition of the KJV has the name of the wrong king, left uncorrected by the KJV translators from the 1602 edition of the Bishops' Bible. The 1611 edition and sixteen more editions of the KJV printed in London have "Jehoiachin" at 2 Kings 24:19 which was later corrected to "Jehoiakim" in most editions of the KJV.