Re: 45th Infantry
The way your inquiry is worded you appear to be referring to the 45th Infantry Regiment but the only 45th Infantry I'm aware of was an element of the Philippine Division and was surrendered in April 1942 when the Philippines fell. I assume you're referring to the 45th "Thunderbird" Infantry Division. If that's the case, the Division Museum in Oklahoma City may have the information you're looking for or may be able to direct you to a source.
"CN Co, 5th Infantry" indicates "Cannon Company, 5th Infantry (Regiment)". The 5th Infantry was an element of the 71st Infantry Division during the war. "Austrian Component" seems to indicate occupation duty.
From what you've given, it would seem he was a member of the Austrian Component, Cannon Company, 5th Infantry, attached to the 45th Infantry Division during the occupation. I have a brief history of the 5th Infantry but there's no mention of the regiment's role (if any) in the Army of Occupation in Europe.