No. And it is anal to specify US. That is the default.
What is more critical is to understand the importance of these declarations. One declares the human readable language of the content, and other declares the character encoding applied to text that is read in. These are technical concerns that deserve due diligence (as in, understanding).
Other lexicons exist within one language. For English there are US, UK, AU, NZ, CA and a host of other Commonwealth countries, but the dialect will not be much different from UK (or AU) on the extreme diction end (mostly the added u). The world has gotten accustomed to both forms, by now. It’s a moot topic. The US form has taken the lead in global terms.
The encoding is what drives the rendering of the document; while the human language aspect is of greater importance to screen readers and other user agents more centered on diction and semantics of the content.