What does this quote mean and who said it in The Witch of Blackbird Pond: a man's first loyalty is to the first soil he stands on?

Nat tells Kit that a person is loyal to the country he or she was born in
because he does not feel loyal to the King of England.

Although the book takes place before the revolutionary war, there are definitely
revolutionary stirrings already.  Kit is a little surprised to learn that Nat has such strong
passions about independence from England, just like her Uncle Matthew.

That would please Uncle Matthew anyway, Kit thought, bewildered and
a little...