Where does English need a lot more effort to say the same thing than another language?

The problem with your question is that it is built on the assumption that English is somehow the default, a natural language, from which other languages diverge. That is absolutely not the case. English is just as exotic to other languages as other languages are to it.

In fact, "mapping semantic distinctions" is going to bring up all sorts of mismatches for any given pair of languages (even fairly closely related ones). The vast majority of these will concern the lexical labelling of categories. Which means that they cannot be easily resolved by lexical borrowing because they concern conceptualisation. For instance, there's no easy way to map the different ways of saying bread between English and Czech. The English category is more general and it causes troubles for Czech speakers of English because they expect a separate words for their fine grained categories. See this list of Czech words that describe something not easy to express in English: http://www.oocities.org/athens/forum/7953/word.html

Prepositions are also going to be hard to map well. For instance, in English you have to conceptualise tree as a container to say, someone is sitting 'in a tree' whereas a language like Czech says 'on the tree'. So you can see, it's a mutual mapping issue.

However, there are also many grammatical distinctions in English that will be difficult for speakers of other languages. They might have to do with definiteness (articles) and the complex system of tenses. For instance, there's no easy way to say in Czech (and many other languages) 'I will have been cooking for 2 hours by the time you arrive.' without significant circumlocution. Conversely, Czech's aspectual system makes it easy to distinguished someone was 'shot and killed' and 'shot and not killed' without ever leaving ambiguity, whereas English always has to specify the outcome or leave it ambiguous.

The list is endless. The semantics of all languages maps onto other languages only approximately once you get out of the sterilised world of logical semantics into the world of real language use.