What can Russians do?
Simply by cutting off all gas exports to Europe.
40% of Europe depends on gas from Russia. Some EU countries have more than 60% of their national energy composition based on Russian gas.
The price of electricity will skyrocket in Europe and part of Europe will be without power, which will cause temporary blackouts, business closures, families will be without electricity, among other generalized consequences.
What does this imply?
The sector that most depends on gas energy is industry.
Highly industrialized countries like Germany, France, Italy, Spain among others, basically those in Western Europe will simply see their industries dwindle.
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And for the US?
The EU is the US's biggest trading partner. Exports to the EU make up 18.7% and imports make up 18.9% of the total balance of trade, this means that the EU alone has a total percentage of 37.6% of US foreign trade.
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Clearly, Americans can withstand these economic effects, but the EU cannot, especially considering the world we are living in with tremendous political instability, high energy prices that can even prevent sanctions, and high commodity inflation in general.