Related: Is it legal in the US/EU to discriminate against hiring Chinese nationals in a tech company that's at risk for Chinese espionage?

No. In fact for many countries the rule is that you can only hire someone from abroad if you've exhausted the local talent pool.

National origin is a protected class in US.

Foreign vs local is not the same as National Origin.

You can't just simply hire anybody from anywhere on the planet if they do not already have permission to work in the US and even then I don't see how someone not currently a resident in the United States would be able to make a play for discrimination on account of being a protected class.

Well, yes, you can't hire people who aren't legally eligible to work for you. But you can't not hire someone who is because they're also a Chinese citizen or look like they might be.

There are plenty of jobs where being an American National is a requirement. For instance many government jobs and anything that requires a security clearance.