Stopping h1b visas will not accomplish anything. The wage differential will still prevail. In my company they have stopped hiring h1bs several years ago and now they are simply moving the work to India. They have not hired anyone all of last year.
But stopping H1-B visas, offshoring, and hiring of non-American born engineers all at the same time because war breaks out will accomplish something. Suddenly the American born male engineer becomes very important again. They will invent many new things because of the huge war time investments made in technology, and after the war America will ride another big technological wave for the next 20 years.