Will Mexico collapse first? Or will the U.S.? Or will they both collapse at the same time, plus or minus a few days? No now knows the answers to those questions; we only know that it will happen, one way or another.
Is Mexico too big to collapse? Can we let it happen? Perhaps we should send them a couple trillion dollars, ha ha. I would save our resources to defend our border from the hordes of destitute Mexicans who will undoubtedly be heading north to loot us of our remaining wealth.
If you have any money left at all, I would invest it in these things, in the order that I list them. You will need: guns, ammo, water, food, clothing and survival equipment, bars of gold (if you lose your guns you can hit someone over the head, and take their guns), silver (same use as gold).
It would also be good to have, car parts, scrap metal, old equipment, miscellaneous electrical parts, basically the stuff that you would find in the front yard of a typical redneck. These items will be used when you need to improvise because what you really need is not available.