In California there are a few rackets that are NEAR 80-90% illegal alien labor in isolated markets (regions) but certainly not statewide and certainly not anything resembling a SKILLED construction trade. I think you are picking from a very unrepresentative sample of tradesmen and projecting your personal experience well beyond the narrow scope from which your data is drawn.
Here in Mexifornia esidential landscaping, roofing those trades have the highest percentage of illegals-------has to be VERY small contractors though as the paperwork to shield the parent firms requires some sophistication. So they just can't be safe for long competing on larger jobs unless they have "protection" from some corrupt politicians or union bosses.
Outside construction there's small manufacturing like cabinetry, upholstery shops, car washes, transient agricultural labor (picking cotton) domestic help (The Nanny and the cleaning lady)------pretty much saturated and overwhelmed with illegal aliens but I seriously doubt we're talking 80-90% statewide.
All of these jobs still have many, MANY Americans beat down by the low wages, lack of respect, lack of benefits and TOTAL lack of bargaining power in their labor market due to the COUNTLESS MILLIONS of invaders from Asia, Latin America, Eastern Europe and whatevers left from there. But the harsh reality is they don't have the aptitude, education, initiative or resources to up and move away to better ground or move up the ladder economically to more competitive job opportunities. America ABANDONS these folks legally and culturally when we tell them------MILLIONS AND MILLIONS of them that they are doing work that American's wont do. Honestly pantmaker this horse shit rhetoric boils my blood.
None of the principles of fair, honest, quality competition apply when the referee is blind, crippled and crazy------meaning he's a political appointee.