According to Statista this is just a statistical anomaly as a result of the Netherlands having such large port facilities - the agricultural products are imported to the country and then exported elsewhere in Europe, which artificially bumps up the export statistics without any correlation to the actual production amount.

Which makes a lot more sense, because even an efficiently-run farming sector surely couldn't be so efficient that it can produce almost as much as the US despite being 1/50 the size. If you look at actual agricultural production the Netherlands isn't at the top of anything - the best they're doing is world #5 in cheese production.