In America, short-sighted means you think in the short term or don't think ahead. So a short-sighted person would accidentally double-book friday lunch, and is only focused on the current quarter's profits.
So "short sighted" is a metaphor in BrE but an idiom in AmE.
At least one dictionary I have at hand says:
myopic |mʌɪˈɒpɪk|
adjective
short-sighted.
• lacking foresight or intellectual insight: the government still has a myopic attitude to public spending.