Well, they both make sense. It's just that the first sentence addressess the user's role whereas the second one addresses the user's identity. The one you should use will depend on which piece of information you wish to emphasize.
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a native speaker of USA disagrees that the first version is not acceptableI assume you mean
a native speaker of the USA disagrees that the first version is acceptableor
a native speaker of the USA disagrees, saying that the first version is not acceptable