Hmmm -- How do we rank the success of other countries that have guest workers? Japan ... Switzerland ... Aruba? What do they do that makes their programs successful?
It's a homogeneous nation.
Second and third generation Koreans-keep in mind, these are people who come from a country that was essentially a colony of Japan for years-are denied Japanese citizenship.
Forget about awarding that privilege to people who come from an even more distant culture.
If America had a system in place like that of Japan-instead of having the most liberal laws in this regard of almost any country on the planet-then perhaps a bracero/guest-worker program might make sense.