Given they and Italy were all part of the Holy Roman Empire and later on with the latter two, the Austro-Hungarian empire such an overlap’s going to be inevitable. There are even German speaking, lederhosen wearing enclaves in Northern Italy. If there are differences, there’ll be differences no matter how subtle they seem (like in Scandinavia).
Switzerland’s famous for being trilingual though keep in mind that the Francophone and Italophone cantons could’ve belonged to either France or Duchy of Milan (Italy) at some point or another. Both Austria and Switzerland are landlocked whilst France, Italy and Germany face seas and oceans.
Whilst Austria and Switzerland used to be part of the Holy Roman Empire, Lombardy and Veneto in recent memory used to be part of the Austrian Empire. Not to mention Austria’s got one of the highest numbers of mongrels in the DACHs region at around 60-70 percent. (Purebreds, if I recall make up 40 percent there but larger* in Germany.)
That’s also shared in France. Also Switzerland, Britain and Norway are outside of the EU.
*May’ve changed now.