> in the US, the letter of the law is all that matters

This is very wrong. In common-law jurisdictions (which the U.S. is broadly-speaking one example of - some exceptions may apply which are not relevant here), judicial precedent is a key factor in interpreting "the letter of the law", which is not the case in continental/civil law. This means that a vaguely-written statute can still provide some meaningful legal certainty in the U.S., where precedent provides some commonly-understood and commonly-developed guidance to what "the spirit of the law" might be; whereas in civil law jurisdictions, overly vague or ambiguous laws can only result in judges and government officials exerting arbitrary power (and in fact this happens routinely!), with not even consistency over time (much less some even more consistent "spirit of the law"!) as a real check and constraint.