Our company just started outsourcing IT 5 years ago. It's still expanding that policy.
While arguably true, it's almost definitely not better conditions to blame. A more likely source is the massive and relatively homogenous US market, a culture open to immigration, and the huge reserves of capital sloshing about the country.
Like, if we take taxes as a percentage of GDP as a figure, the US scores pretty well at about 27%. But Australia is at 28%, Canada at 32%, and even the UK at 33%. The differences aren't massive here. He'll, Ireland comes in at 23%.
Even a high tax state like California would have a five figure amount less owed in taxes than Ontario at certain income levels.
I remember being told over 10 years ago as I was entering the field of software that I shouldn't bother: my job is going to be outsourced soon enough.
This is just a scare tactic with little teeth. Not to say it doesn't happen, but it doesn't happen enough for it to be a consideration.