Look in the "Game / Data / Sound / Speech" folder, and you will see nine numbered folders, each full of ogg vorbis sound files. If you temporarily de-activate the mod, and cut the "Sound" folder from inside the MODS folder structure, and move it somewhere for safe-keeping, then re-activate the mod, you should then have the Stock game ogg vorbis files, which by default are English language - unless of course, you installed the German voices...
All that said, in OMEGU, I am almost certain there is an add-on that restores English speech to the German side, ~and~ if I am remembering correctly (this is doubtful at times...

), if you play the US side with OM enabled, you should get English voices anyway... maybe... lol - let me tell you, it is really fun getting older, because every day is a new adventure!