This is a complex question and there is no accurate or correct answer!
For me it's Spain for sure because if you become allies with the Southern/Northern United States, then you don't have to worry if they get defeated because there are no other countries around them except Canada which they can destroy at an early stage, then make some army and proceed to Europe. The first country they pass through is Spain which means that while SUS/NUS are destroying Canada you can try something on France without any worries. Why? Because SUS/NUS are just behind you and even if they don't want to help you that much, they MUST because otherwise they can't proceed properly in Europe if France destroy you.
That's mostly for the early game, but you'll have bigger advance later!

Yes but embarking/disembarking takes much valuable time.

Venetoo

I do well with Turkey cause there is only 1 playable nation bordering you.

I'm only on my fifteenth game- having played 7 in tutorial, 7 in 39 historical, and 1 on endgame 44. Of those maps, the one most similar to clash of nations is the tutorial. There my best three results were with Sweden, Caucus and Southern US ...

The corners are usually the best but I would have to rate as FAVORITE Turkey, Tsar, and Caucus
Egypt has a bigger economic problem than the others. Spain is interesting but if France starts to immediately fortify the border and is allied with Italy and or England you are in trouble.

Honestly, I never choose. All the countries feel the same other than Russia. Russia has food issues and takes a long time to go around

If you are new to the game, I would highly recommend playing Morocco.
Morocco gets pretty high resources and is well defended, only having one bordering player. On day one you should attack the ai to your left and prepare to invade spain. Be sure to ally yourself with Algeria since he will protect you from the east. South USA may attempt to invade you, so leave a reserve army. If South USA attacks within the first couple days, he/she probably won't be able to support the invasion, let them overextend and then push them back into the sea. By day 2 you should start invading spain. After cleaning up spain, most of the players will go afk and become ai, giving you most of europe to invade.

Russian Empire is so big that u take time to get from one place to another. Uk and african states take time to embark/disembark a lot. France-Germany-Poland are too vulnerable. Spain gets attacked by african or American States easily. Sweden and Finland are too much naval. If I have some good navy, I can destroy whole of them. America is very far. Yugoslavia, Italy, Caucasus and Turkey are among the BBest.

I wouldn't recommend Morocco, partially because of the economic problem (shortage of food and goods coupled with a severe manpower shortage), but mainly because of its position on the map. If you don't make friends with Algeria, they could attack you, and even if you win this attack, you need to worry about Spain, France, Southern US, Libya, and even Italy.

There's an issue with this.

The truth is most of the Clash of Nations 22 player map is that all of the countries, in a very, very generalized way, have mostly the same resources. It all comes to doctrines. What I recommend is not one specific country - branch out. Try different doctrines, and see what works for you as a player.

Still, some personal picks:

Sweden. Well located, easy access to a new city or two, and not too many immediate threats, as well as decent sea access.
Italy. Again, excellent sea access, a nice gathering of potential allies, and plenty of room to expand.
Canada. Only one immediate threat, which can be befriended. After that, explore Europe to your heart's content!

Finland is slept on. It's got a booming economy, and it's near the corner without being too big like Green Russia. It borders 3 AI nations and 2 player nations, but Sweden's border is far from its production zones, and Communist Russia's border is a choke point where you can concentrate a few units in a fort. This is significant since defenders have an advantage in the beginning with everything being infantry.

The likely course of action is to take/befriend Sweden after you've built some subs and take/befriend Red Russia. Poland, Ukraine, and Germany are also some potential parters for a two front war against your neighbors (my favorite strategy).