The letter, sent on Sunday, amounts to the strongest known written warning from the US to its ally.
It says Monday's attack on Aitou raises "real concerns" with respect to international humanitarian law.
Recent polling indicates Trump is having success with both groups, in part due to his message on the economy.
The group is alleged to have made fake labels from famous French vineyards, using them to sell cheap wine.
India and Canada expelled diplomats as tensions rose over last year's killing of a Sikh separatist in Canada.
Travel agency-organised pub crawls will be banned in the Czech capital at night, the council says.
The Apprentice, which focuses on Trump's early years as a real estate tycoon, is released this week.
The German airline has agreed to pay $4m to resolve claims it discriminated against Jewish passengers.
The tech giant says it will use energy from small reactors to power its use of artificial intelligence.
The Hollywood star discusses fatherhood, The Godfather and playing chess.