Yes, I think so. It was his tweet on Monday when he took credit for the move by Saudi Arabia and some other Arab nations to cut diplomatic relations with Qatar. He claimed that it was his visit to Riyadh, his strong support for going after Iran, and supposedly his demand that these nations stop financing terrorists. I think he is right. I do not think these nations would have made this move without this strong support from Trump, who supported the move in his tweet as well, although we cannot be sure about this. But Qatar had not done anything recently to newly aggravate the Saudis and others. Indeed, most reports have that it provides no state support for terrorists and has made some moves to crack down on private citizens doing so, although perhaps not as much as some other Gulf states, but more so than Kuwait, which has not had its diplomatic relations cut. And while the Saudis have claimed that Qatar is too friendly with Iran, in fact the Qataris have 1000 troops in Yemen helping the Saudis fight the Houthis, who are supposedly supported by Iran.
Of course more recently Trump has been offering to have this dispute settled or negotiated by one or another of his top national security officials, most of whom were in Australia when he made his tweet. If they had had advance warning of his tweet, they might have pointed out to him that Qatar hosts the main US air base and CENTCOM in the Gulf, from which US planes combatting ISIS take off. Probably they did get around to pointing this out, which may be why he is now offering to help negotiate a solution. But I suspect that the Qataris are not too keen on using his good services for this.
I also think that his visit and statements triggered the killing of protesters in Bahrain right after the visit and also the arrest of several thousand people in Egypt. Both of these nations are among those joining Saudi Arabia in cutting diplomatic relations with Qatar. What I am not sure of is whether his visit had any connection with the ISIS attack on Tehran, probably not, but who knows? Of course his statement of "sympathy" to Iran has been outrageous and received as such by the Iranians. And while Trump and the Saudis and the Israelis claim that Iran is the leading state sponsor of terrorism in the world, the most recent estimate has about 94% of terror attacks being carried out by Sunni Muslims, not Shia ones such as the majority of the population of Iran is. And, indeed, this ISIS attack on Tehran has been reportedly carried out by Iranian Sunnis.
Oh, another place where Trump may have had some influence is on the outcome of the British election. He is very unpopular there, and while maybe the Tories would have lost anyway, May's strong identification with Trump certainly did not help her, especially with him also making an outrageous and inaccurate tweet attacking London Mayor Khan, and then doubling down on it. It is not out of the question that this last shenanigan may have been the straw that broke the back of the failed Tory effort to retain their majority in Parliament.