Donald Trump is unlikely to address parliament when he visits the UK next month over fears that the Commons Speaker’s opposition to the idea could cause an embarrassing row.
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Once the timetable for Trump’s trip is agreed, usual protocol would dictate that Buckingham Palace should then request invitations for the US president to address parliament from Bercow and Lord Fowler – Bercow’s counterpart in the House of Lords.

However, government sources suggested that although no final decision had been made, a request was unlikely to be put forward on this occasion because it would probably be turned down and could potentially embarrass the Queen.

https://www.theguardian.com/us-news/2019/apr/30/donald-trump-not-expected-address-parliament-uk-state-visit-bercow