Evain also says he is concerned that some fans were prevented from bringing flags into the Dallas Stadium at Sunday's match.
The venue will host England's opening game against Croatia on Wednesday.
"You were not really allowed to bring a flag in, or at least to show it, which is inconsistent with most Fifa rules and regulations, but also what was allowed at previous tournaments. That seems to be closer to what is in place for NFL games," he said.
"At a lot of the stadiums it hasn't been a problem, so it's hard to understand what is the actual policy and what is improvisation by the staff locally with the rules that they now have.
"Most of the flags were removed by the staff. The broader problem - and I think it's a demonstration of how much Fifa has little control over this tournament - is that there's no consistent rule, and when you look at what Fifa has published, there's a code of conduct that is very broad.
"But it never clarified a lot of things, like what sort of symbols are allowed and not allowed? Are you able to bring a flag of your region or city or club? A lot of this is still up in the air, and I think there's a bit of learning by the venues, but also, again, inconsistency."
In its tournament guidance for fans, external, Fifa says that "small flags, banners and posters made of a fire-resistant material are allowed in the stadium. Larger flags, banners, posters or instruments must be approved in advance."
It also prohibits flags "that are of a political, offensive and/or discriminatory nature".
On Monday, Fifa won a court hearing in Los Angeles that means Iran supporters are banned from taking pre-revolutionary flags into their matches, classifying it as a political symbol. However, Evain says some non-political flags have also been confiscated from fans by stadium staff.
"It is just this lack of clarity that is hard. You should know the rules before leaving home, and that's not the case", he said.
"The main issue at this stage is the absence of rules. It's very unclear what is allowed in the stadium. What you can bring, what you can't bring. Your flag, your bag, your drums, your banner", he said.
"What we are probably looking at is a tournament where the rules are going to be extremely different from one venue to another - which is not how it should be.
"Fifa seems to have failed to apply rules across the board. And what we've seen in Dallas, it seems that the staff's understanding of the rules of the tournament has more to do with what is usually allowed in an NFL game than the actual code of conduct implemented by Fifa."
Fifa has been approached for comment.
