I suspect you're exaggerating.

That's more than enough to make Kiwi dialect unintelligible to other anglophones and qualify it as a distinct language. You could not have avoided using a few of those words in your post, the way words of French origin like very, use and question have become unavoidably common since the Norman invasion.
It would be fun to see some of these words. Why don't you start a thread and post some, like the one going about the differences between British and American English?
The English of the Southwestern U.S., which was once Mexican territory, is full of Spanish words but they don't make our dialect hard to understand. Most of them are for local things that don't even show up in our speech when we're out of our own territory, such as
arroyo (properly spelled
arrollo) for a normally dry ravine cut through the desert by flash floods, from the same root as
desarrollo, "development."
Other Spanish words of more general usefulness have penetrated the American language to the point that any Brit, Aussie, South African, etc. who has seen our movies or TV shows is probably familiar with them. A few are pronounced more or less correctly, like
sombrero, a wide-brimmed hat for shielding from the desert sun, from
sombra, "shade." Some are mispronounced outside Aztlán (the trendy new name for the region coined by a "Latino power" movement that ran out of "power" as its members assimilated to the disgust of their fashionably alienated leaders), such as
rodeo--we say roh-DAY-oh, you say ROW-dee-oh. Others have been hopelessly mangled in the process of anglicization, such as "lariat" for
la reata and "buckaroo" for
vaquero (one who herds cows, from
vaca, "cow").