Remember that all passengers go through customs and immigration at the first landing in the USA, even if on a direct flight to another USA destination. On flights to the USA, it can thus be desirable to find a nonstop flight from somewhere overseas to the USA destination--i.e., connect in SCL rather than LAX/MIA/JFK etc. Some international gateways are widely reputed to be far worse than others, with MIA considered to be very bad and LAX/JFK considered bad (although at LAX some USA carriers have their own customs and immigration facilities rather than arriving at TBIT and then changing terminals for the domestic connecting flights).