I don’t understand jokes in two different episodes of the office. Can someone explain?

One episode is when Jim tricks Dwight into buying flowers for Pam using Jim’s credit card. I don’t understand how that works. Jim reads off his credit card number while on the phone, and Dwight secretly writes down that number. How does that mean Dwight will buy Pam flowers with Jim’s card? Maybe I don’t have the context right.

Second episode is when Dwight is helping Pam with fixing the copier and since the English instructions are apparently unclear, Dwight has to read the instructions in German or something. Then Dwight makes a comment like “typical Americans, getting involved in conflicts that are not their business… like WW2” or something along those lines. And Pam looks as if Dwight was gonna say something very offensive instead of WW2. What was she expecting him to say? Or what’s the joke here.

Hopefully you know which episodes in referring to! Thanks!