The telegram was sent to Mexico in an attempt to set up Mexico to attack America so that Americans didn't enter the European war
US foreign policy today is hard to describe as its changing with the election of trump but lets say that we were observing the time a bit before this and more in the present-day era.
We used to stay neutral will all countries we could but we began to see that it was not always best to stay neutral (as in the case of WWI and WWII). The failed attempt after World War I to make a league of nations that operated well just demonstrated the problems we had, and was the reason why WWII happened and adolf hitler was able to come to power.
Today, we use economic and military forces on places that are labeled unstable to try and make these places more stable and set up a democratic government.
This for the most part, has failed miserably such as in Syria and Iraq.
Again, mods, please write me if you have concerns over links but I find students learn best sometimes from visuals. This video describes the problem that happened in Iraq/Syria that led to the failure of US troops trying to make the government more stable.
https://www.youtube.com/watch?v=AQPlREDW-Ro
This second video goes more in-depth about the Syrian crisis and shows how US foreign policies affected it.
https://www.youtube.com/watch?v=RvOnXh3NN9w&t=12s
