So what’s your idea about stopping this invasion?
At this point, since none of these people are at the border, I would use it to wring the necks of Mexico and central America to force them to deal with it or cripple their economy. Ratchet it and suspend the ability of their people that are here to send money to Mexico or these other nations. Then I would start to cut them off diplomatically. Close the embassy there. Close the consulates here. Freeze the assets of those nations in the U.S.. Impose massive tariffs.
Basically I would not let this crisis go to waste.
The ones that still approach the border will be met by a security fence similar to what Hungary used at key points, manned by the armed forces that will utilize all weaponry (various riot control systems that have been employed overseas), short of live rounds, to fend them off. Those that may break through will be captured by a secondary line of troops that will NOT be there to escort them to anyplace other than awaiting troop transport planes that will then directly fly them back to their starting point. If any of those nations wish to see a penny ever again, they wont refuse us landing.
The cost of fuel will be extracted from the cut-off aid or from the assets seized.
From there I have the Geo-political situation I want. Troops on the border, aid cut off, and these nations at my mercy. From there this is when the serious border wall gets constructed with the troops there permanently, and negotiations start with Mexico to get a permanent security situation in place before diplomatic relations are normalized, trade resumes, and their assets are unfrozen.