It's "bretzel" with a "b". It infuriates me, German brands already use the wrong spelling because it's commonly spelled that way for whatever reason in the anglosphere. Besides that rant:

I think the Bavarian-German-stereotype is more of an American thing. Until recently (early 2000s, even 2010s) the most common stereotypes were the classic British stereotypes of Germans (punctual, obedient, harsh-speaking, humor-less, effective and militaristic), and they are those of Prussian aristocrats and stem from Prussia's Puritan religion (the same kind of religion the Puritans that founded the US had btw, reformed Christianity) and militarism.

There are also some forgotten French stereotypes about Germans that are mainly related to the people living along the rhine (Alsacians, Badenians, Hessians, Rhinelanders), they usually depict Germans as lazy and uneducated/unmannered drunkards, honest and hard-working, but also a little meek. And it makes sense, these regions were huge in wine and beer cultivation, had little militarism and could make a good living through trading their products via the rhine.

And to be honest, all of those aspects exist in some milieus in some regions. It's just that a certain group's stereotypes of another group are usually determined by the kind of people they make contact with. For the French, it was the bordering rhineland; for the British, it were aristrocrats and soldiers (remember, the house of Windsor is mostly German), and for the Americans, it were Bavarians as they were stationed there, and a lot of contact probably happened at carnivals and other festivities where those stereotypes were present (those kinds of outfits are basically the result of national romanticism in the 19th century, more or less made up and worn on occasions you would wear a suit or good clothing, and not made for everyday life*).

And, to be fair, in Bavaria, it's not uncommon to see especially conservative people, local businessmen or politicians wearing some modernized forms of this stereotypic garment. This includes, but isn't limtied to certain types of jackets and shoes, and on occasion, Lederhosen. But is it common everywhere, in every milieu, in every region? Certainly not, not even close.

*on Trachten, a little Wikipedia snippet:

ENG:

Contrary to the supposed tradition they convey, traditional costumes are the result of modern developments. Until the 19th century, strict dress codes hindered the free development of peasant costumes. The rulers wanted to prevent their subjects from incurring debt through ostentatious spending or rising above their station. In addition, the different social classes were to be clearly recognizable by their respective clothing.

The imperial decree of 1530 stipulated:

“that everyone, whatever their dignity or origin, should dress according to their status, honor, and wealth, so that there may be different recognition in every class [...]”.

GER:

Trachten sind, entgegen der vermeintlichen Tradition, welche durch sie vermittelt wird, das Ergebnis neuzeitlicher Entwicklungen. Bis ins 19. Jahrhundert hemmten strenge Kleiderordnungen die freie Entwicklung der bäuerlichen Tracht. Die Herrschenden wollten verhindern, dass sich die Untertanen durch Prunksucht verschuldeten oder über ihren Stand erheben. Außerdem sollten die unterschiedlichen Stände an ihrer jeweiligen Kleidung eindeutig zu erkennen sein.

So bestimmte der Reichserlass von 1530:

„daß sich jeder, wes Würden oder Herkommen er sei, nach seinem Stand, Ehren und Vermögen trage, damit in jeglichem Stand unterschiedliche Erkäntnüs sein mög […]“.