Is it common in any other first world countries besides the US to work while attending university?
In Germany, at least one survey reports that 47 percent of students work during the semester, and 63 percent work during the holidays between semester.

Most of these students earn less than 500 Euros a month, but 6 percent earn more than 1000€ after taxes. Over 60 percent that have jobs have one to finance their studies/living expenses. For 7 percent of students, their job is their only source of income. 

According to the Sozialerhebung 2012 (a large survey by a federal agency)  figure 9.10, 13 percent of students studying towards their first degree  worked more than 20 hours a week on average in 2012. Whether that's "common" is a matter of interpretation. 

The part on financing reports a median income of 300€ from working, with 63 percent of students doing some kind of work. Figure 6.5 shows that 2 percent of students only finance through studies through work, with an average income of 960 Euro, and 13 percent mainly finance their life through working, with an average income of 660 Euros. 

(All sources in German)