I'm searching for evidence that the US government, in the lead-up to the Civil War, considered British investors might fund a transcontinental railroad through the Southern States. Thank you.

During the period between the end of the Mexican War and the start of the Civil War (1848-1860) leaders in the South actively sought a transcontinental railroad that would link their states to the Pacific via Texas, the New Mexico Territory, and California. I'm a historical fiction writer who is looking for evidence that the US government considered British investment in this project a credible threat in the decade or so prior to the US Civil War. Thank you.