I’m pretty sure alot of languages just imported marshmallow.
I come from the german speaking part of Switzerland and I don’t think I ever heard someone actually use the word “Mäusespeck” although it certainly would he understood I think. Everybody around me calls them marshmallows.
For me "Mäusespeck" are smaller marshmallows that usually come in white and pink and in different shapes. Sometimes the shape of a mouse. Marshmallows are the larger white and cylindrical or cube ones that you put on a stick to roast on a campfire before eating.