If this is in regards to WWII, then yes, I would say that fighting in 2 such different areas will be difficult. In fact, even Adolf Hitler himself had one of the great fears of being attacked from both western Europe and Eastern Europe when the war began, and thus, it is why he tried to attack so viciously.
The US on the other hand also did not want to have to split troops to be fighting both in Europe and the Pacific when Japan became a part of the Axis Powers. The US actually tried quite hard not to get involved and put themselves in that position. Congress passed a series of Neutrality Acts in the late 1930s, aiming to prevent American citizens from trading with nations at war, loaning them money, or traveling on their ships. The US then entered the war in Dec. 1941, and was eventually able to help turn the tide of the war with the Allies. A large reason the US was able to be so successful fighting in two parts of the world was that of their immense population, resources, and military strength (not to mention the atomic bombs).
Hope this was helpful!