There is a travel ban on Haiti and Iran travellers to the United States of America, which means the fans are ban from coming to United States of America to support there teams, that will definitely be a minus for both team,
But the question is since there is a travel ban on travellers the question is will both team be allowed to play in the United States of America in the 2026 world cup?
Due to FIFA rules, USA has to accept federation people, meaning that while it's true that travellers, like regular people, can't go, Iran could easily create credentials to a thousand people if they want to, and send them there. Not sure if they really want to, doesn't mean they may want to, they may feel okay with this, after all how many teams will have tens of thousands of fans in every game, only the big ones, smaller teams usually do not have that much, I remember in Qatar, there were many games where it was just Qatari people watching it.
But the rules are rules, so if federations of those leagues wants to send anyone, and have the finances for it, they can create the paperwork to send, just like how players are capable of going, the federation "workers" will too, and these could be hidden fans with no real work, just getting fake papers.
I believe you are underestimating how different this will be compared to Qatar. In Qatar, when one country did not bring 20-30k fans, then it was largely a matter of money, distance, or interest. They could go; the vast majority of them simply preferred not to. Here, for Iran and Haiti, it's the opposite: a chunk of people would literally sell everything to follow this team... and aren't allowed in the country at all
Federations can fool around with fake titles, all right. However that does not resolve the underlying emotional disconnect:
- Haitian fans on the island finally see their team back at a World Cup after 50 years and still have to watch from home while Little Haiti in Miami throws the party
- Iranian players strike in front of mostly diaspora who have been protesting the regime over the years. In Qatar the regime brought in 300 or more loyalists to drown that out. In the US, those guys are exactly who the system is built to filter out
Even if they bring a bus full of “staff”, the feeling stays the same: for people in Iran and Haiti, this World Cup is on TV only, not in real life at the stadium. The noise of the stadium will be there, yet so many of the people it belongs to are on the wrong side of a border