Its what’s not in the food like additives, preservatives, pesticides, gmos and growth hormone. EU has stricter regulations.
You can buy the same food here.
> EU has stricter regulations.
Different, not stricter perse. In the EU it is allowed to sell food with non-edible parts inside or cheese with maggots.
Not stricter, just different emphasis. For example, the US famously has stricter controls on bacterial contamination than much of Europe.