"There are critical differences between where we are today and where we were then," said Amos Hochstein, who coordinated Iran oil sanctions for the Obama administration.
"The first and most important is that Europe is not following with their own embargo, their own sanctions on energy, which means that for the first part of the sanctions implementation, you won't have this big takeoff of Iranian oil — 650,000 barrels — that will come off the market even if the European companies do comply," Hochstein told CNBC's "Squawk on the Street" on Wednesday.
U.S. law allows countries to continue buying Iranian oil so long as their home country significantly cuts overall crude imports from Iran. The Obama administration asked countries to reduce oil supplies by 20 percent every six months.
If the Trump administration follows that model and European countries do the bare minimum to comply with the sanctions, it would take six years to shrink European purchases to zero, Nephew estimated in a recent report.
It is possible that another event could head off a trade dispute between Europe and the United States. Iran could grow frustrated and abandon the deal.
Europe and the United States could also find a face-saving way to revise the nuclear deal. Trump's demands include placing permanent restrictions on Iran's nuclear activity, expanding inspections, sanctioning its ballistic missile program and addressing its role in Middle East conflicts.
Some analysts say that is simply too much for the Europeans to concede.
"We're asking for the moon across a whole range of activities and we're giving them very, very little," Nephew said. "I can't believe that that's not going to backfire at some point."