Comment by ifwinterco

I think it's because the US has the clout to indirectly compel foreign institutions to cooperate in a way that other western countries can't.

For example, for a US expat living in the UAE the various branches of the US government can threaten the UAE government, banks etc. to make them cooperate and tell them how much the US citizen is earning to ensure they pay their US taxes - if you're a bank anywhere in the world, you do not want to be cut off from the US dollar system.

If the UK, France, Germany etc. tried to tax their citizens globally it might work in other western countries, but in places like the Middle East they might struggle to get foreign entities to comply making it impossible to enforce.