Fortunately, he can be, just as Trump is. Each country makes up its own rules about who is or is not a citizen. The US can't allow itself to be whipsawed by other countries' laws.
Remember, it's the same with Trump. He's a national by virtue of the circumstances of his birth of both the United States and Great Britain. But as Americans we can't concern ourselves with what Canada or Great Britain do or we will forever be at their mercy.
The framers put in “natural born” to put a premium on a certain type of citizenship.
Why else include it ?
-Each country makes up its own rules about who is or is not a citizen. -
You are confused. Being a citizen is not that same as being a “natural born” citizen in the context of the late 18th century.
Read about natural law, which the Constitution is based on.
Actually, I think there is a clause in British law that the child of a British-born mother cannot claim British citizenship unless it is of good moral character. That would knock trump out of the running.