I am arguing there is no clear break at which you can reach a consensus. Suppose groups that had reached the Americas before Columbus, such as the Norse, proba

I am arguing there is no clear break at which you can reach a consensus. Suppose groups that had reached the Americas before Columbus, such as the Norse, probably Polynesians, possibly others, had settled in large numbers instead of just a fleeting contact, and that had happened repeatedly since the first peopling of the Americas, and some of the groups had merged with earlier groups, and some had not, then how would you define a native American? This is exactly what you have in the UK. I notice you have ignored my comment asking you to provide a clear definition of native British. Given that most saves of immigration to the UK have merged into existing populations do specify how much of people's ancestry needs to be whatever you call "native" for it to count.