If President Obama has committed an impeachable offense why hasn't any Republican member of congress filed ?

No one has filed articles of impeachment because there are no grounds to do so. Sadly too many people listen to and believe the garbage spewed out by FOX News and the right wing radio talk shows to their detriment. People need to educate themselves on what is really going on in the world rather than believe spokesmen for the Flat Earth Society like Sarah Palin. Obama has done a fantastic job. If not for his economic reforms the US would be in abysmal shape, far worse than anyone could probably imagine.