Technically Poland.
Poland first, then every other European country except for UK, Ireland, Sweden, Switzerland and Portugal.
Hitler first annexed Austria.
The US did not exactly invade Germany. Maybe you are referring to when the Allies invaded France which the Germans had occupied.Some say the US first crossed the German border at the Remagen Bridge. However, earlier, the 85th Cavalry Reconnaissance Squadron, a unit of the 5th Armored Division, crossed the border but returned back to their unit.
Norway
who was the first country to invade in world war 2
Germany.
Phillapines
poland
Technically Poland.
In the Second World War, the first country Italy invaded was France, in 1940.
In World War 2 the Allies attacked Axis controlled Europe. The first place they attacked was the island of Sicily.
Poland first, then every other European country except for UK, Ireland, Sweden, Switzerland and Portugal.
POLAND!
Serbia, their tiny next door neighbor whose intelligence service had backed The Black Hand, the organization which assassinated the heir to the Austrian throne. This was the cause of the conflict. It was Russia's decision to meddle in this affair on behalf of the Serbs which embroiled their French allies, and also the Germans as allies of the Austrians.
Hitler first annexed Austria.
The Allies first landed in Libya, then later in Italy.