i know someone that works in construction on the management side in the midwest. he said the illegals will build twice as fast and as good if not better than the american workers.
I wouldn't trust someone who doesn't speak English to do proper electrical work in a house, much less the stuff that really skilled electricians do (industrial, high-voltage, etc.)
My house was rehabbed by a guy who clearly used cheap immigrant labor as much as possible and in many places it shows. I've had some issues with plumbing, a bathroom cabinet that was just screwed into drywall rather than anchored, a lot of little things like that. There's a difference between hard working (which a lot of illegals are) and skilled. There are of course plenty of shitty American plumbers, electricians and drywall installers, simply being from the US doesn't prove anything.
One thing I've noticed is that if you want to make a good living in the trades you have to be a competent small businessman. If you're working for someone else you're no better off than a white collar wage slave.