Answer by Tom Goodwin:
Modern US immigration law.
For a country that was based on those seeking a better life, it's extraordinarily hard for most of the world to move to.
For example as a Brit:
You can't enter the green card lottery.
You need either a H1B or O1, or L1 or another extremely hard Visa to work there. ( for example the window to get accepted for the easiest Visa is open for about 4 hours in a year)
It's then even harder to actually move there permanently and have rights.
Which doesn't really make sense to me considering.
1) The nation is sparsely populated.
2) There is a surplus of homes that need to be sold and huge stretches of the nation with depressed economies.
3) The economics of immigration are shown to do wonders, especially if you using a rules based system around age, education and health.
4) It's not like the US has an expensive benefits system that could cause people to move there and become a drain.
5) The US population is ageing and China looks likely to overtake it's economy this century.
So what is there to fear with new arrivals? especially younger, more educated, richer, healthier people?