hmm , it could be an idea to have Canada , Australia , New Zeeland and UK as the Commonwealth
dunno , maybe some more isles that also have Elizabeth as their Queen , call it personal union but she is technically the head of state for those countries.Also Cyprus has 2 UK bases.Gibraltar and Falklands could be done too.
USA should get Mexico and South Korea , also Diego Garcia and Kabul.
i would ignore Taiwan and make it a barbarian island to give China some action.
For problematic spots like Israel , if you choose to make ... make 2 cities .. Jerusalem and Tel Aviv
and base about 30 merchants there so they can support a huge army.Also Jewlers corp.Or have USA pay them 600 gold per turn for oil. ... and use less merchants.
New York , London , Hong Kong and Tokyo should all have about 20 merchants.Moscow ,Rio .Paris ,Berlin , Beijing ,Johanesburg and Cairo should have 10 merchants too.
remember to add 1 carrier groups for Brazil (or Mercosur) , India and Russia.
2 carriers groups for EU and Commonwealth and 10-12 for USA.
No carrier for China but many subs and destroyers.Japan same as China.
Russia should have about 3 times as much tanks as USA or EU .China should have 3 times more infantry. USA should have 5 times more air forces then next civ.
Expeditionary armies like Spenatz (Chechnia),French Legion(Chad) ,SEALS and SAS(Iraq and Kabul) should have a lot of experience , eg Leader and 30 more xp.
also , remember that you dont need 18 civs , prolly 7-8 big civs and 3-4 small ones.(Israel ,Pakistan ,ASEAN ,Ukraine , Egypt or African Union , Saudi ,South Africa )
some barbarian cities for Cuba ,Venezuela ,Colombia ,Serbia ,Kosovo, Albania,Iraq , Iran(- or civ) ,Afganistan ,Cechnia ,Daghestan ,Tibet ,Yemen ,Siria, Somalia ,Sudan , North Korea ,Taiwan ,Nigeria , Mali , Chad ,Zimbabwe ,Uganda and Rwanda ... just to keep us peace keepers busy

just dont over do unit numbers , better use 3x20 xp upgraded SAM inf/anti-tank/machine gun. than 10 riflemen.