Actually, I think the country that built the intercontinental railroad was Russia, seeing that the Trans-Siberian Railroad runs from Europe into and across Asia.
Or maybe it was Britain, which completed a rail link between Africa and Asia by building a railroad bridge across the Suez Canal in 1918 for the Palestine Railway.
The majority of the Union Pacific track heading westward was built by Irish laborers, by Mormons who constructed much of the track in Utah, and after the war by veterans of the Union and Confederate armies. Chinese immigrants did most of the work on the Central Pacific track. Most White men received between one and three dollars per day, but workers from China received less and were supervised by Whites. Eventually, the Chinese went on strike and gained a small increase in salary.