The 1965 Hart-Cellar immigration act is not a "natural flow" of people that just happened to stumble their way into America. It's a deliberate act to limit European immigration and create massive inflows of non-European immigrants into America. This was why Emmanual Cellar fought the 1924 Origins act for 40 years to finally overturn it in 1965. With the help of Jewish advocacy organizations as discussed in Kevin McDonald's Culture of Critique. Modern nations-states in the West have border enforcement and travel restrictions. They have entire beaurocracies dedicated to enforcing borders and facilitating mass immigration. People are prevented from coming and going every day. There are passport and visa systems to ensure the right people are allowed to come and go where they are allowed to go. There are hundreds of NGOs which receive state and private funding via donations to facilitate mass immigration, feed them, house them, and help them find jobs. Nothing natural about it.