What European country did US fight against?

Nazi Germany (Tripartite Pact signer)

Fascist Italy (Tripartite Pact signer)

Slovakia (Tripartite Pact signer)

Romania (Tripartite Pact signer)

Hungary (Tripartite Pact signer)

Yugoslavia (Tripartite Pact signer)

Bulgaria (Tripartite Pact signer)

Transylvania (Tripartite Pact signer)

Croatia (Tripartite Pact signer)