In a true race to the bottom like that, the American is out of a job regardless.

>the American is out of a job regardless

yes if the American can't find their competitive edge.

How can you, an american, with a family, mortgage, car payments etc., compete financially with someone from a "shithole country", who's willing to work for very little money and live on a bunk bed with 7 roommates in a two bedroom living container? (literal situation currently in my company)

Life is about trade off, if the American want to be paid more in order to have all that then they better provide more value for their employer compared to someone from "shithole country"

The question is really why a voter would vote for representatives that would allow for that situation to occur in the first place?

Whatever situation you vote for there always a trade off.

But why would it be in any voters interest, for the government to let cheaper workers in, that bring the wages down?

some voters may be interested in the reduced business cost by the ability to hire cheaper worker.