What is the meaning of “these lederhosen are riding up my Bundesliga”?

The meaning of the sentence is, "These lederhosen are riding up my butt." It's supposed to make kids watching the film giggle (and some adults, like me). The filmmakers didn't want to use the word "butt", so they chose a word that starts with "B" and sounds distinctly German ("Bundesliga") and is possibly familiar. They used that word instead. They expected the audience members' minds to replace the word when they heard it. Notice that the penguin who says the line is pulling his lederhosen out of his "Bundesliga" as he's saying it.

There is no commonality at all, except these are words the audience may or may not be familiar with (less so Bundesliga and more so lederhosen) But more importantly, sound german...which is what they were obviously making fun of. German is often made fun of for how it sounds in English speaking media. Tim Allen Gives a good example.

Of course they're making fun of a very specific german stereotype, namely the Bavarians, with the lederhosen and lesser so the accordion.

But if you wanted to really pull something from nothing, FC Bayern Munich is a top Bundesliga team.

This is an example of the Gratuitous Foreign Language trope.

In English, the word "Bundesliga" sounds vaguely like "bunghole", which is a word often substituted by children for "butthole". So the joke is that the lederhosen are riding up his butt.

For example, "bunghole" was used extensively in Beavis and Butthead: