Another meme based on my headcanon about the Crystal War. Once again, As that alternate timeline was based on World War 2, particularly America and the Western Front, Sombra's attempted interdimensional conquest of the Human World would be likened to the Eastern Front of World War 2 and the colossal failure that followed in it's wake. His invasion of American soil would be the Crystal War equivalent of Operation Barbarossa. Like Barbarossa, this operation ends in failure due to his unfamiliarity with Humans and the Human world as well as poor planning due to severely underestimating the fighting strength of the Militaries of the Human countries on Earth.

I think that it would take two months for the Military to be able to gather enough forces to launch a counterattack because they were caught off guard due to Sombra having the element of surprise, most of their forces are overseas or not present in the region of the US Sombra had invaded through. In that time, he'd be brazing through and conquering a significantly large swath of territory and bloating his army with mind-controlled Humans.