Has there ever been German opposition to Hitler based on him being Austrian? I know that there are Bavarian-Prussian/South-North issues in Germany, but did the North Germans not have an issue with a naturalized citizen from so far south that it crosses the border creating such a fuss in their country? Was there never such issues?
When Austria was invaded and annexed, did Austrians regard Hitler as an Austrian or as a German? Was there any kind of "he's one of our own" sentiment or was Hitler basically a German to them?
Hitler's citizenship was actually a huge problem for much of his early life. For one thing he was basically a draft dodger from the Austro-Hungarian military, which he did not want to serve in. Instead, before WWI he lived in Germany where, on the outbreak of war, he volunteered for service in the German military. After the war he did not acquire German citizenship, but obviously played a key role in the politics of Munich immediately after the war, particularly his part in the Beer Hall Putsch, which was actually a terrible failure.
Ian Kershaw in his biography of Hitler points out repeatedly that by all accounts Hitler's career should have been ended over and over again whether by being deported back to Austria or for his violation of his parole following his release from Landsberg or any number of other reasons and that his continued success and ability to stay in Germany was a combination of luck, sympathy for his cause on the part of various state officials, and to a certain extent the recognition that he had served in the German military even if he was not a German citizen.
In 1925 he renounced his Austrian citizenship but, again, did not acquire German citizenship. Hitler was technically stateless until as late as 1932 when he began his campaign for the German presidency against Hindenburg. He finally acquired actual citizenship by being appointed to a position granting citizenship by an NSDAP minister.
Sources: see Hubris: 1889-1936 by Ian Kershaw.