It is true that this difference is not universally recognized. However, let those who make assertions such as "Americans never use 'shall'" peruse a good US English dictionary, or many US legal documents which often contain phrases such as:
• Each party shall give one month's notice in writing in the event of termination.
Note that exactly the same rule applies in the case of should and would. It is perfectly normal, and somewhat more elegant, to write, for example:
• I should be grateful if you would kindly send me your latest catalogue.