I see where you're coming from, but in practice offering location-agnostic salaries means you're not competitive in areas that command higher salaries (notably, large tech hubs like the Bay Area, Seattle, New York). If anything, you're trading the talent pool near those hubs (and let's be honest, the rest of the US) for talent in other countries.

That's a trade-off you might be willing to make, but I hope you understand that not every company is willing to write off the entire talent pool of the US.

(As a point of reference, the only two countries that Google pays comparably to even the cheapest parts of the US are Switzerland and Israel.)