The usage of interest happens in the meaning of what is best for the nation (or the nation according to the one using such word). Its a rather vague concept that can both mean and put weight to a lot of other concepts and ideas.
The other use for the word may be in the sense of interest rate, a term from economy that means the extra cost that is put upon debt or such.
Examples of interest being used:
"Voter interest in the midterm elections has surged to records within both parties (...)"
"(...) US Fed raising interest rates (...)"
Answer:
The most important discussion for U.S. national interest.
Is the USA versus China commercial war, a matter of interest?
Wall street eagerly waits for the new Interest rate Fed is going to announce.
Dow Jones feels the aftermath of higher interest rates, announced by Fed.
Explanation:
1) In the sense of a concern, the word interest can be used to express a common concern to some people, especially in geopolitics but also in internal affairs.
Example:
The most important discussion for U.S. national interest.
Is the USA versus China commercial war a matter of interest?
2) In the sense of the profit/cost of an investment. It's also a point in many debates.
Wall street eagerly waits for the new Interest rate Fed is going to announce.
Dow Jones feels the aftermath of higher interest rates announced by Fed.
