FILE - This March 22, 2017, file photo shows a family having a picnic on the bank of the Rio Grande river in Miguel Aleman, Tamaulipas state, Mexico, located across from Roma, Texas. President Donald Trump will face many obstacles in building his “big, beautiful wall” on the U.S.-Mexico border, including how to pay for it and how to contend with unfavorable geography and the legal battles ahead.  (AP Photo/Rodrigo Abd, File)