But none have come from the large Western European powers that have been cornerstone US allies for decades. Instead, Mr Trump has courted and been courted by Central and Eastern European leaders.
For Mr Trump, the region offers the potential for new trade, energy and military arrangements that can sometimes circumvent Western Europe and tweak traditional leaders, such as Angela Merkel.
"We have a great relationship. We have a big trade business going on," Mr Trump said at the start of his Oval Office meeting with Mr Iohannis. "We buy, they buy."
Before the meeting, a senior administration official said Mr Trump is highlighting "the importance of Central Europe to the United States, both as allies and security partners, and as business and commercial partners for the future," a senior administration official said on Monday.
Mr Iohannis, who also visited in 2017, praised Mr Trump and what he called the "right path" of relations.
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"We have the opportunity to talk about our very good strategic partnership, and under your strong leadership we progressed, and we will continue doing so," Mr Iohannis said as Mr Trump looked on approvingly.
Mr Trump also gave Mr Iohannis a plug as he heads to elections this fall, saying he thinks the Romanian leader will "do very well."
The trip was timed in part to seek Mr Trump's blessing, seeing it as a political boon.
"Some of the Eastern European leaders, whether Hungary, the Poles, and now Romania, have basically figured out how to deal with Trump, and they appeal to some of his more illiberal instincts," said Kelly Magsamen, vice president for national security and international policy at the Centre for American Progress.
"Trump likes the idea of undermining the European project, whether it's Brexit or anti-EU feelings," shared by Mr Trump and some leaders he has invited, said Ms Magsamen, a former national security aide to both presidents Barack Obama and George W Bush.
Mr Trump has met with the leaders of Britain, France and Germany overseas in 2019, but not at home. He will see close allies at the annual Group of Seven meeting this weekend in France, and is expected to soon invite new British prime minister Boris Johnson to the White House.
Like other presidents, Mr Trump takes advantage of overseas meetings such as the G7 and G20 to hold rounds of meetings that diplomats call speed-dating. Those meetings are typically shorter and less involved than a formal White House visit, which is usually the product of months of planning and internal jockeying for a spot on a president's crowded calendar, veterans of other administrations said.
The emphasis on Central and Eastern Europe echoes a similar effort at post-communist outreach under Mr Bush, but it comes in the different context of rising nationalism across the continent and cracks in the European Union. It also contrasts sharply with Mr Obama, who forged an especially tight bond with Ms Merkel during the global financial crisis a decade ago.
Mr Iohannis himself is not hostile to the EU, as Mr Trump is, and has criticised neighbour Hungary's swing towards anti-immigrant nationalism. But he is seeking Mr Trump's blessing as he goes to elections this fall and was eager to accept a coveted White House invitation.
Mr Trump wants to point to Romania as an example of Nato nations meeting their pledge to spend 2 per cent of gross domestic product on defence. Romania may also join Central European neighbours in opening or considering diplomatic missions in Jerusalem, a Trump administration priority after the United States broke decades of precedent to relocate the US Embassy in Israel from Tel Aviv to the holy city also claimed by Palestinians as a capital.
"This is an area that's very exciting; there's a lot going on there. Economies are growing. Trade between these countries and the US is increasing all the time," said the administration official, who spoke on the condition of anonymity under White House protocol.
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Daniel Fried, a former senior State Department official and ambassador to Poland, sees "mixed motives" in Mr Trump's focus on Central and Eastern Europe. Mr Fried, now a Europe specialist at the Atlantic Council, applauds the effort to draw these nations closer to the United States, even if "the ideological wing of the Trump White House likes them for the wrong reasons."
The Trump administration has especially sought out Poland, seeing it as a counterweight to German influence and priorities. Mr Trump has mused about relocating some US forces now stationed in Germany to a new headquarters in Poland, and will make his second visit as president to Poland over Labor Day weekend.
Western European diplomats shrugged off questions about whether their leaders feel slighted or at any disadvantage for the emphasis on generally poorer and less powerful nations.
Both British and American officials note that with the selection of Mr Johnson, a pro-Brexit conservative, Mr Trump now has a close ideological ally at the helm of one of the major Western allies.
French president Emmanuel Macron has stepped back from his role as the face of European efforts to talk Mr Trump out of punitive trade policies and confrontation with Iran. The two leaders were cordial, if a bit stiff, when they met on the side-lines of events commemorating the 75th anniversary of D-Day in June.
"We're doing a lot together, and the relationship between you and I and also the United States and France has been outstanding," Mr Trump said before he and Mr Macron met in the French city of Caen.
Ms Merkel has been pointedly critical of Mr Trump at times, including last month when she said his attacks on four Democratic lawmakers of colour run counter to what she considers "the strength of America."
"There have been opportunities for the two leaders to see each other outside of the White House this year," a German official said.
Ms Merkel has visited Mr Trump at the White House in both 2017 and 2018, but Mr Trump has not visited Germany as president. He is deeply unpopular in Germany.
Asked about Mr Trump's absence from Germany during the White House session on Monday, the administration official dismissed the notion of any slight to Ms Merkel.
"President Trump has frequent contacts with Chancellor Merkel, and this should not be read into any meaning for the US-German relationship," the official said.
Ms Merkel herself may have been studying up for her next meeting with Mr Trump, or perhaps just throwing a bit of shade with her reading selection on vacation this month.
Photographers captured Ms Merkel reading Harvard professor Stephen Greenblatt's Tyrant: Shakespeare on Politics, which former Bush administration State Department official Eliot A Cohen reviewed as "fundamentally a book about President Trump."
The Washington Post