Glad you liked them - some ideas for uses:
1) The party has a lot of coins from Kingdom A. Nobody will take them and they have to get them exchanged for gems or deal with the black market.
2) The party gets paid with counterfeit coins, and then get caught with them (or told the coins are counterfeit)
3) Marauders from country A attack where the party is, threatening to leave no survivors to prevent reprisal.
4) Between adventures, at the local tavern the party is listening to the latest songs. Town guard shoulders their way in, threatening to arrest everyone, and at least hauling in the local bard. The party either needs to convince the guards they were innocent bystanders or face fines and threats not to repeat the songs/tales they just heard, or possibly face imprisonment.
5) While shopping, local thugs trash the shop and/or harrass the shopkeeper about their loyalty to "the wrong country". Or the party needs something from a local individual only to find out they've been taken in for questioning/loyalty testing.
6) A war profiteer (
@Whizbang Dustyboots ) seeks to hire the party to stir up trouble and have it blamed on one of the countries - or possibly try and draw the 3rd country into the conflict
7) A NPC asks the party to rescue someone whose been unjustly abducted by one of the rival kingdom's forces (or a misguided group claiming loyalty to one)
8) Party is asked to thwart an attempt by one of the two countries to create an alliance with a powerful, spiteful creature that could shift the balance of power (A dragon, a sphinx with knowledge of a powerful war spell, a pack of griffons that could be used as flying mounts, etc.)