They walked across the Bering Straight, which was a land bridge at the time
combined vertical and horizontal integration
That’s the Monroe doctrine, which basically said that the Americas were closed to anymore colonization from European powers.
There were lots of foreign changes that presented challenges for the US. I'll give you a few examples from different time periods. First would be when England wanted to tax the Americans in the Revolutionary period. They did this to try and restrict America's freedom. Another example would be that Russia had spies during the cold war period. This was to gain intelligence of the US war plans. Also when Germany sent the Zimmerman Telegram to Mexico during the WWII period. This was to get Mexico to launch a surprise attack on the US.
major events of the early years of the civil war from 1861-1863:
The Civil War began. The South had advantages as they were better prepared, had better war plans and generals. North was not well prepared and did not have good generals to command their soldiers.
Major events of the middle years of the civil war from 1863-1865:
As the war dragged on, the advantages of the North from having more factories and better economy showed their effects to the various battles. Key victories for the North at Gettysburg, Forts Henry and Donelson .
Major events of the ending years of the civil war after 1865:
After Gettysburg and Lincoln's Emancipation Proclamation, the South recognized it was losing the war. Cities of Petersberg and Richmond were taken by the North. The South retreated further and further. Even after Lincoln was killed in an assassination in 1865, the South had lost and surrendered.
