Appearing during a trip to Washington DC on Fox & Friends, the breakfast show on Fox News, Johnson gave a positive account of Trump's record in office.
Johnson said: "You've got to realise that the American president is just one of the huge, great global brands, and he is penetrating corners of the global consciousness that I think few other presidents have ever done.
"His method of tweeting early in the morning, no matter how rambunctious those tweets may be, they are communicating with people. And yes, a lot of people don't like it but a lot of people relate to it."
The remarks come with Johnson facing controversy at home over comments about Nazanin Zaghari-Ratcliffe, a British-Iranian woman serving a five-year jail term in Iran.
Johnson said Zaghari-Ratcliffe had been "simply teaching people journalism" when she was arrested - contradicting her own account of being on holiday.
The comment has been pounced on by Iranian figures as proof of what Zaghari-Ratcliffe was really doing in the country.
Discussing Johnson's political appeal, a Fox News presenter said during the interview: "Boris you were made for television - I like the way you turned in the middle, thought about things, you are just a great guest. Thanks so much for joining us."