why the audience laugh?
Here is a transcript of one TED talk, I am confused by the reason that the audience laughed when the speaker said " it's kind of like America wanted workers, but then, they got confused when we got people instead. " Is it funny? Why?
_________
You know, people that come to the US in search of jobs as laborers, or field workers, dish washers. You know, things that we might consider low-wage jobs but the immigrants? That's a good opportunity.

The news nowadays has convoluted that whole thing quite a bit. You could say that it's made America's relationship with immigrants complicated. And as immigrant expert George Borjas would have put it, it's kind of like America wanted workers, but then, they got confused when we got people instead.

(Laughter)

Question

why the audience laugh?
Here is a transcript of one TED talk, I am confused by the reason that the audience laughed when the speaker said "  it's kind of like America wanted workers, but then, they got confused when we got people instead. " Is it funny? Why? 
_________
You know, people that come to the US in search of jobs as laborers, or field workers, dish washers. You know, things that we might consider low-wage jobs but the immigrants? That's a good opportunity.

The news nowadays has convoluted that whole thing quite a bit. You could say that it's made America's relationship with immigrants complicated. And as immigrant expert George Borjas would have put it, it's kind of like America wanted workers, but then, they got confused when we got people instead.

(Laughter)

Answer

The audience laughed because the speaker made a joke at America’s expense. According to the speaker, "Americans" welcomed immigrants as workers, but became confused when they discovered that the immigrants were actually people. (Well obviously, workers are people.) This kind of anti-American rhetoric is very common in America (and, luckily, perfectly legal, unlike in many countries), and some snobbish Americans who consider themselves better than their countrymen seem to really enjoy insulting other Americans. It’s sad they don’t appreciate how wonderful America really is, or even value their freedom of speech and other privileges of living in the USA.

Answer

Not having watched the TED talk (or even knowing what exactly it was about) I can only guess.

America wanted the labour; they didn't take into account that the people doing the labour 
a) come with their own language & culture and
b) don't disappear when leaving the job for the night
In other words, they're living among them, but they're not quite like them, and that scares them a little.

The fact that that didn't occur to them beforehand can be seen as entertaining (and more so if presented well).

Answer

The audience is laughing because the idea that workers were needed or desired and then when the workers were available, employers were surprised they were actually humans. The employers were so "dumb" they did not realize the workers would be people. -People who have feelings and needs. It is funny because the workers were obviously going to be humans.