Interesting scoop by Axios on Salazar being vetted as US Ambassador to Mexico. Less impressive is the usual Beltway tendency to tie Mexico’s relevance for the US to just border security.
Tensions in the US-Mexico relationship go well beyond border security and are reaching a boiling point. Just take a look at several agriculture disputes
https://www.postregister.com/farmandranch/crops/potatoes/letter-raises-alarm-over-u-s--mexico-food-and-ag-trade/article_6e099b5c-b622-54d0-a39a-e34a3f7a1ca5.html

Human rights in Mexico is another area of high tension with the US government these days. Any new US Ambassador will have to thread carefully here. Again, you cannot just reduce the US-Mexico relationship to just border security. https://thehill.com/policy/international/545756-mexico-president-censures-us-over-state-report-critical-of-human-rights
And lets not forget...energy! The Mexican Govt’s legal changes have created a conundrum that the Biden administration will have to deal with sooner rather than later. A new US Ambassador will arguably have this as a top priority (not just border security) https://www.uschamber.com/press-release/us-chamber-warns-proposed-changes-mexico-s-electrical-industry-law-could-create
Perhaps the most obvious fact that many Beltway reporters tend to forget when thinking about Mexico is that the size of US trade with Mexico rivals that with China & Canada every single month. It’s not just border security. https://www.freightwaves.com/news/mexico-regains-status-as-no-1-us-trade-partner