On Tuesday morning, toward the very top of a White House press briefing, national security adviser Jake Sullivan made a statement: "After a lot of commentary in recent weeks about the state of the transatlantic relationship, the United States and Europe head into these two summits aligned and united on the major elements of the global agenda."

Sullivan went on to tick off broad efforts the U.S. and EU are working on together, aimed at combatting the ongoing COVID-19 pandemic, climate change and the push for a favorite Biden administration goal: a "rules-based international order."

But the fact that Sullivan had to stand in front of the press and make the case that all is well before President Biden heads to Rome for the G-20, and then Glasgow for a major U.N. climate summit, underscores just how bumpy the past few months have been for an administration that campaigned on the promise of restoring respect and order to the United States' key alliances.

It's a far cry from June, when Biden glided through a parade of handshakes, hugs and smiles during his first trip abroad as president. Allies from other G-7 and NATO countries could barely contain their delight that the roiling, rocky Trump era had ended and that the American president once again prioritized coalitions and alliances.

"America is back," was Biden's constant refrain throughout the meetings.

The America-is-back vibe was best summed up by Biden's chummy seaside meeting with French President Emmanuel Macron at the G-7. Macron — who had memorably exchanged multiple, seemingly endless handshake competitions with Biden's predecessor, former President Donald Trump — smiled and told reporters, "I think it's great to have a U.S. president part of the club, and very willing to cooperate."

Just about ever since then, "the Europeans have certainly witnessed a series of very poorly executed policy decisions that required strong allied consultation and engagement, and yet were completely lacking," argued Heather Conley, a former State Department official and a senior vice president at the Center for Strategic and International Studies.

That includes a submarine deal that roiled Macron to the point that he temporarily recalled France's ambassador to the U.S. A make-good meeting with the French president is one of Biden's top priorities when he arrives in Rome this week.

The issues causing problems between Biden and allies

Conley pointed to three key tension points stemming from Biden administration policies.

First, that the U.S. was much slower than the rest of the world to fully reopen borders due to COVID concerns. Nonessential travelers — with proof of vaccination — will only be allowed into the country in the coming weeks.

German Chancellor Angela Merkel pressed Biden to move faster during a summer White House visit. It was a rare note of discord on a visit that otherwise underscored the closeness of the U.S.-German relationship.

Next, and most important, was the chaos and violence stemming from the withdrawal of American forces from Afghanistan.

NATO allies with a presence in the country had to scramble to get their citizens out as the Taliban swept into Kabul. High-ranking officials in Germany, the United Kingdom and other key allied nations blasted the decision, though Biden repeatedly insisted that everything was fine. "I have seen no question of our credibility from our allies around the world," he said during an August press conference.

Then, there was a surprise deal with the U.K. and Australia to share highly secret nuclear submarine technology, a move seen as a way to counter growing Chinese power in the Pacific.

The problem was that it led to Australia cancelling a massive submarine contract with France, catching America's oldest ally completely by surprise. When France's ambassador to the U.S., Philippe Etienne, blasted the decision to NPR's Morning Edition, he could have been describing Europe's complaints about the Trump administration.

"There is the lack of transparency, there is a breach of trust," he said, after he had been temporarily recalled to France. "There is unpredictability. But there is also inconsistency."

Biden has worked to patch things up with France, and will hold a one-on-one meeting with Macron in Rome on Friday. (Vice President Harris will travel to Paris next month to continue the effort.)

Conley argued all this has led European allies to wonder how much they can count on the U.S. anymore, even with the turbulent Trump years currently behind it. "One problem is recoverable. I think two begins to become a pattern," she said. "And then the third strike — then countries begin to make some different decisions about how they're going to cooperate with the United States. And I think that's where we are."

And that leads to the high global stakes of the second half of Biden's trip: a major climate conference in Scotland, aimed at speeding up the emissions-reduction goals first set in Paris six years ago.

Biden has called for major greenhouse gas cuts by the end of the decade — a halving of the country's carbon footprint — with the ambitious goal of a net-zero economy by mid-century.

Biden's climate clout depends on Congress

Scientists agree the world is fast running out of time to head off the worst of global warming. But the legislative package that would have achieved most of Biden's end-of-decade goals has been massively scaled back — and is still being negotiated.

Biden's climate envoy, John Kerry, warned that showing up in Scotland with no deal would be devastating for American credibility, especially after decades of broken promises. He told the Associated Press the hit would be as bad for the country's image as when Trump withdrew the U.S. from the 2015 Paris agreement.

Kerry later walked that back, as did Biden. Sullivan insisted on Tuesday that allies aren't doubting Biden's commitment to tackling climate change.

"I don't think world leaders will look at this as a binary issue: Is it done? Is it not done? They'll say, is President Biden on track to deliver on what he said he's going to deliver? And we believe one way or the other, he will be on track to do that," said Sullivan.

What that track looks like, and how exactly it lowers greenhouse gas emissions so quickly remains unclear, without the Clean Electricity Performance Program that had been the centerpiece of the legislation's climate program.

Still, Todd Stern, the Obama administration's climate envoy, generally views Glasgow like Sullivan does. "I don't think that countries are going to think, 'Oh my God, the U.S. isn't doing anything.' I think they'll be worried, for sure," he said, if Biden arrives at the conference without a legislative framework in place.

Stern said that mindset, however, assumes some sort of legislation gets passed — even if it takes longer than Biden would like, and would do less than Biden first wanted. If the deal fully falls apart, Stern conceded the U.S. reputation — and Biden's climate clout — would become a "huge issue."

So the most important part of Biden's trip will probably be striking some sort of agreement before Air Force One takes off for Rome on Thursday.