No-one can sue the EU - but anyway any settlement or imposed damages, and the hellish court fees, would be from tax-payers' money!
Your esteemed President comes over as clumsy, tactless, ignorant and desperately inexperienced in his dealings with foreign politicians, but a bit of conversation I overheard by chance yesterday, made me ponder its suggestion that Mr. Trump is not as stupid as his speeches and behaviour makes him seem, but is wily and intentionally divisive.
The cynical side of me suspects that he respects only three national leaders: Messrs. Kim*, Putin and Trump, but as a foreigner it's very hard to determine what he does think of my and other foreign countries.
*KIM: In at least some Far Eastern cultures, the family name precedes the individual's name.