I think the argument was that at any given level of compensation, being an international worker motivates you more. So the fact that compensation can also motivate people misses the point.

Is there an argument why being an international worker would motivate you more other than attempting to get a higher salary than you can locally? I don't want to use the words "desperation", but it seems as if that is the impetus to hire international workers, who are desperate for US wages without being protected by US labor law (in most cases, you're going to operate as a contractor in your home country when employed by a US firm, without labor protections you'd have as a US or local country employee). It is a hack by US corporations around US market wages and labor protections, one that I'm unable to endorse until labor protections apply to the business relationship.

When losing your job means getting deported it can really sharpen your sense of focus.

Don't worry though, it's not just immigrants to the US. I emigrated from the US and to be completely honest I still work hard but not with the underlying worry I always had just a little bit of before I secured my status more permanently.