You can use these tags to switch between countries during non-ironman singleplayer games. Press Tilde(~) and then type "tag XXX" and hit enter, where XXX would be replaced with the below 3 letter tags.
Germany = GER United Kingdom = ENG Soviet Union = SOV France = FRA Italy = ITA United States = USA Japan = JAP Sweden = SWE Norway = NOR Finland = FIN Denmark = DEN Iceland = ICE Lithuania = LIT Estonia = EST Latvia = LAT Romania = ROM Yugoslavia = YUG Serbia = SER Greece = GRE Albania = ALB Bulgaria = BUL Hungary = HUN Croatia = CRO Slovakia = SLO Poland = POL Luxembourg = LUX Belgium = BEL Netherlands = HOL Czechoslovakia = CZE Austria = AUS Portugal = POR Ireland = IRE Switzerland = SWI Spain = SPR Afghanistan = AFG Iraq = IRQ Oman = OMA Iran = PER Saudi Arabia = SAU Turkey = TUR Yemen = YEM Egypt = EGY Syria = SYR Lebanon = LEB Jordan = JOR Libya = LBA Australia = AST New Zealand = NZL Bhutan = BHU Tibet = TIB Nepal = NEP British Raj = RAJ Phillipines = PHI Siam = SIA China = CHI Guangxi Clique = GXC People’s Republic of China = PRC Shanxi = SHX Xibei San Ma = XSM Sinkiang = SIK Yunnan = YUN Mongolia = MON Mengkukuo = MEN Tannu Tuva (All Hail!) = TAN Korea = KOR Liberia = LIB Ethiopia = ETH South Africa = SAF Canada = CAN Mexico = MEX Costa Rica = COS El Salvador = ELS Guatamala = GUA Honduras = HON Nicaragua = NIC Panama = PAN Cuba = CUB Dominican Republic = DOM Haiti = HAI Brazil = BRA Argentina = ARG Chile = CHL Colombia = COL Bolivia = BOL Ecuador = ECU Paraguay = PAR Peru = PRU Uruguay = URG Venezuela = VEN
Any nations created after the game starts will be given a tag D## with the ## ascending based on when the nation was created (i.e. Nationalist Spain, one of the first nation to be created, should have the tag D01).