I read in a history of the movie western that at one point in his career the films of Roy Rogers were more musical than western. That was never more true than in describing Hands Across The Border. Republic might well have just dispensed with the plot and made this one a western musical revue.
The film has all kinds of numbers done by Roy Rogers, Sheila Terry, the Sons Of The Pioneers, dancing by Janet Martin and the Wiere Brothers and comic relief by Guinn Williams and Mary Treen. Even the sequences involving Trigger could just as easily been worked into a revue.
The very thin plot has cowboys Rogers and Williams hired by Joseph Crehan a ranch owner with a lovely daughter, Sheila Terry. Crehan and rival owner Onslow Stevens are competing for an army contract to sell cavalry horses. This mind you in an age of mechanization. Crehan gets killed trying to ride Trigger, but it's Roy who eventually rides Trigger and saves him.
Onslow Stevens's part is strange as well. He's built up to be the bad guy as he usually is. But when the film is over all this guy really has done is pay some attention to Sheila Terry in an effort to get that contract one way or another. He never really does anything all that villainous except look like one.
The last quarter of the film is simply a reprise of all the numbers that had been done before in the film. Later on Roy's films got a little more action in them. This one probably disappointed the kids.