Translation:The Netherlands has twelve provinces.
Originally, the Netherlands was a republic, consisting of seven provinces. Currently, however, we are a kingdom, totalling a slightly bigger number of provinces, and a bunch of countries that are technically distinct/not subject to Dutch rule, but history and legal ties still exist.
'The Netherlands' is plural. The Dutch translation for it, however, is 'Nederland', which is singular. This has carried over into the English language and you use the verb 'has' instead.
I guess perhaps because the country of the Netherlands is meant here and not the Kingdom of the Netherlands. Just like the UK consists of several consituent countries, The Netherlands is a united kingdom aswell. With the country the Netherlands as the main one. Confusingly unlike in english the (unoffical) names match (officially it is Kingdom of the Netherlands). (Though with the UK it is confusing that the language is named after one of its constituent countries, which has the result that any one from the UK quite often incorrectly is called an Englishman. (And in dutch people often called the UK simply England)
Ow yea the other constituent countries are: Aruba, Curaçao,and Sint-Maarten (not st Martin which is French and not a country). Suriname used to be one of them but became independant in 1975. And the Dutch Antilles as a whole used to be. The other islands (besides Aruba and Curaçao) and considered special municipalitis of the Netherlands (Saba, St Eustatius and Bonaire) they aren't constituent countries).
Or by similar logic. It is the country that has 12 provinces and not the (historical) collection of low lands (which the Netherlands got its name from) that have the provinces.
In short the kingdom has subdivisons and the (collection of regions that provided the name of) country had subdivions and it is not the subdivisions that have the provinces but the country