It apparently was British soldiers who inspired Herta Heuwer to create the dish in the late 1940s, so there is definitely an indirect SA influence.
The döner kebab, which has long overtaken brats in popularity for a quick snack, is even younger - 1970s.
Interesting. I thought the curry spices would have come with the Turkish immigrants. My parents, from Hamburg and Nuremburg, came to America 90 years ago, as adults. The spice shelf in my childhood home contained just cinnamon, mild paprika, black pepper, salt, MSG, cloves, and bay leaves.
THE mustard we use? I assure you, WE use a wide variety of mustard on our hot dogs. Not sure what youre basing your observation on.
Our fried calimari often has hot peppers mixed in. Sometimes called Rhode Island style.
I’m going to wade in here (at the risk of self-flagellation) but I think one candidate is Danish cuisine.
At least the dishes that I’ve tried, as an admitted neophyte and newbie to Danish food, were never spicy (which does not mean they were not flavorful, because they were).
Dishes like stegt flæsk or frikadeller are not spicy, though they are quite flavorful (esp. stegt flæsk topped with persillesovs), and of course Danish pastries are never spicy. 
I am happy to be proven wrong.
I will sit down now.
Thank you.
But they do appear to have an interestng history, according to Wikipedia.
First appearing around 1850, when Austrian scab labour was brought in to the country to replace striking Danish bakers.
Another vote for midwestern US cuisine. Grill a steak and you better not put ANYTHING other than a bit of salt & pepper on it. And maybe not even that.
Everything else = S&P only. No herbs. Maybe mirepoix if you are making soup & using a recipe. If fish is on the menu, then it’s usually pan fried with a bit of cornmeal in the flour & you guessed it, S&P. All proteins were served with boiled potatoes and a vegetable and/or an iceberg lettuce salad with tomato & cucumber and bottled dressing.
And if there is one single red pepper flake in a dish, someone will notice it. 
Did the Austrian bakers introduce cardamom to the dish?
I’ve no idea.
Does it have cardamom in it? I’ve just done a quick Google, looking at the first half dozen or so recipes. Only one, an American recipe (King Arthur ?) includes it. The other ones appear to be European (well, the ingredients are in metric) and don’t have it.
Hospital food.
Must be an American viewpoint that cardamom is the taste of Danish pastries.
Not necessarily Bone. I did a bit of Googling yesterday evening and, apparently, its use is not uncommon in Scandi baking.
Maybe the Vikings brought cardamom back from Istanbul, according to this.
In Sweden, cinnamon has been available since the 1300s for a few, and since 1731 for it to be more common. https://www.thelocal.se/20190104/how-spices-have-connected-sweden-with-india-since-the-viking-age
