North Korea & North Vietnam.
Germany
the two countries are the US. and Saudi Arabia.
Washington was at war with Hanoi.
British,France, Russia
Germany and Austria-Hungary
You have to tell us which two countries you mean so we can answer this.
The two countries that border the US is Canda (to the north of the US), and Mexico (to the south of the US).
Iraq and Afghanistan. We are not officially at war with Iran, and do not have permission to fight in their country against Talliban. Iraq and Iran
The US was still recovering from WW2. The Soviets had just tested their first A-Bomb in 1949. With two countries with the "bomb", both enemies...it was not a time to fight a war.
us and Canada are two different countries
The United States fought both Cuba and Russia to fight the spread of communism. One effect of this was the Cold War which lasted through much of the 1950s and 1060s.