This geo-balancing approach described makes little sense.
"It was a lot cheaper to hire a $200K/year engineer in our American offices than to pay someone the equivalent compensation in any of our European offices."
This is not a very good frame of reference to take though ... they are getting paid $200K - what they give to their government is their business, not yours.
If people are paying 'higher taxes' well hopefully they get some benefit from that. If not, well, it's their country to work with.
If you consider that that European may be getting big retirement, more vacation, free Uni, free Healthcare, free Childcare etc. - well - then that's kind of 'part of their comp'.
Also, Supply/Demand is a thing.
True 'Geo Balancing' would imply paying the person what their market rate is, in that market - and - if you're based in a market with higher salaries you can actually pay bit more (i.e. this the 'Supply' part).
I guess what I mean to say is ... the 'comp' should be what goes to the staffer + payroll taxes. In the US it's a small amount. In France, it's a lot.
So you basically end up paying someone in a 'high payroll tax country' less - all other things being equal.