This one seems to be 100% USA, and then spread over social media. The same as Valley-speak became really popular after Clueless came out in the 90s. I can't recall seeing 'welp' anywhere before 2017.
I just checked my chat history - I used it in 2013, and there's a huge flood of "welp" from my chat partner between 2015 and 2019. (In 2020, the ball is on my side of the court again, it seems. Welp.)
Yes, I speak english as a second language since grade school... And never stumbled upon this word until recently. This is the first time I read the actual meaning, also. Had no idea what it meant.
