My girlfriend and I are thinking of doing a vacation in Mexico early next year while I am working in the US.

I will be in the US around 50% of my time this year for work on a Visa waiver, that means like 6 weeks at home in Germany and then another 6 to 7 weeks in the US, which should be fine.

In January we are thinking to take some days off and meet in Mexico for a vacation.
She would fly from Kansas City to Mexico and I would fly from Germany with a connection flight to the US and then with another connection flight to Mexico, after a week I would fly back to the US and stay for some weeks for work.

Now I am concerned about the USCIS, since I have to go through immigration and be afraid that there could be complications since I technically have been in the US (only for the connection flight) and be back within just one week, especially because I would have been in the US this year a lot of my time.

Does anybody went through a similar situation or has any info?

I would ask a lawyer for an answer. That sounds tricky to me...and I think you should get this answer for free. And to feel good call another one for a second opinion. I did this very often.Good luck