I'm not going to answer the question exactly, but I'm just going to show the difference in gastronomy between the different countries of the world by showing you images from the "Hungry Planet" exhibition, whose members show what they eat by week:

1-Germany

2- Norway

3-Japan

4- Italy

5- Chad

6- Kuwait

7-USA

8-Mexico

9-China

10-Poland

Hello 

"I did not hesitate to answer this difficult question". And yes, the dish, common to all countries in the world. Vegetables, fish, meat, noodles, onions, fruit, cabbage, even pebbles, namely: 

  

Soup !!!!!!! Universal dish, which is consumed at any time of the day, all year round. Dish loaded with childhood memories, soup of yesteryear appreciated by our elders...

List the countries I know or visit in no particular order.

 Indonesia: Indomie

 Singapore: Chicken Rice!

 Malaysia: Nasi Lemak

 Thai: Mango Sticky Rice

 China: Small Basket

 Japan: Sushi

  Korea: Chajanmyung

 Czech Republic: Branbolak

 India: Chicken Tikka Masala

 Turkey: Kebab!

 Hungary: Kurtoskalacs

 Netherlands: French fries and Mayooooo

 Switzerland: Cheese

 Germany: Currywurst

 Belgium: Chocolate

 Italy: Thiramis

 USA: New York Cheese Cake

 France: Escalgo

 Greece: Gyro

 UK: Fish and Chips :)

 Poland: Pierogi

 Vietnam: Fo

 Hong Kong: Egg Waffle

 Taiwan: (but no food) Bubble Tea

 Mexico: Nachos

In the countries, I know, and for my personal tastes, what best represents Vietnam is pho (sorry, I don't have Vietnamese diacritics on my keyboard): 

 

In Thailand, my preference is tom yum: 

 

In Cambodia, I have a weakness for amok trey (fish curry): 

 

This one, I cooked it myself, which explains the somewhat odd appearance.

And in Taiwan, the world-famous 牛肉面 (beef and noodle broth):

Argentina: Asados   

Azerbaijan: Plov

Bahamas: Cracked conch 

Barbados: Cou cou and flying fish 

Bhutan: Ema datshi 

Brazil: Feijoada 

Bulgaria: Shopska 

Cambodia: Fish amok 

Canada: Poutine

Chile: Curanto 

Colombia: Bandeja paisa 

Comoros: Langouste à la Vanille 

Croatia: Peka

Cuba: Ropa vieja

Cyprus: Koupepia

El Salvador: Pupusa

Estonia: Verivorst

Equatorial Guinea: Succotash

Ethiopia: Doro wat

Fiji: Kokoda

Gambia: Domoda

Georgia: Khachapuri

America: Hamburger

Japan: Sushi

China: White rice

Russia: Borscht

UK: Spotted dick*

Taiwan: Bubble milk tea

Canada: Maple syrup

Mexico: Taco

Italy: Pizza

Greece: Olive oil

Sweden: IKEA meatballs 

Pakistan : Biryani 

India: Pani puri 

Bangladesh: Hilsa 

Sri lanka: Kottu roti 

There are so many others famous dishes in this countries but most famous dishes the these..