It might, but that doesn't seem to be the reason, I think the musical style predates the Germanic invasion of Texas. Tejano music is heavily influenced by Musica Norteno, the music of northern Mexico. Not sure where that style got the "Oompa" sound, but I agree. It reminds me of the "Six Fat Dutchmen", a polka band of the Minnesota/Iowa/Nebraska/Datkotas area from the 1950s and 60s.
It was influenced by German polka music --- the same musical instrument the accordian is used. The lyrics are often very different though --- they're not like "Roll out the barrel" but about drug smuggling and that popping sound you often hear is about shooting law enforcement agents.