Final answer:
The false impact statement among the options is that immigrants were treated better due to their labor in building railroad tracks, as immigrant workers often faced poor working conditions, similar to domestic workers during the industrial expansion era. Option d. is correct.
Step-by-step explanation:
The impact of the railroads on the United States was enormous following the Civil War. While they did indeed stimulate other industries, lead to the emergence of new cities, and cause major cities to specialize in certain industries, the claim that immigrants were treated better because of their labor in building the tracks is not accurate.
The railroads did require vast amounts of labor for their construction, which often included immigrant labor, but this did not necessarily translate into better treatment for immigrants. In fact, immigrants often faced long hours, low pay, and unsafe working conditions, similar to domestic workers during the industrial expansion.