It's hard not to get angry at the company when you see them hiring at median US wages ($100-120k US equivalent) but specifically refusing to hiring folks in the US, when the company is US-based.
Mexico City, especially -- general consensus is that the level of expertise is good, it's not hard to find a Spanish speaker in the US, better cultural fits, and the timezones overlap better; MXC is on Central Time. Not India-level cheap, but competitive enough.
Canada is even better in that sense, but at a higher price.
NAFTA TN visas are also attractive there, too. No H1B nonsense, and can easily bring personnel over for short (~3 year) tours.
Disclaimer: USA-ian of Hispanic extraction in Canada, so I follow these gigs reasonably closely.
You also don’t have to pay for healthcare of your Canadian employees since they pay for it on their income taxes.
Plus, London alone has 10 million people, and if you lump in the London commuter belt that adds up to aroun 15 million people, more than all of Ontario! That's a hell of a skilled worker base to work with.