と言（い）える is a common expression that utilizes the potential form of the verb 言（い）う ‘to say’, to highlight that it is possible for something to be said. This phrase is often used to express a general idea about something that the speaker believes to be correct.
と言（い）える translates as ‘it is fair to say (A)’, or ‘one could say (A)’.
As the 格助詞（かくじょし） (case marking particle) と is being used in its 引用（いんよう） (citation) use,
と言（い）える may follow any direct phrase/statement.
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この儀式（ぎしき）は日本（にほん）の文化（ぶんか）の一（いと）つと言（い）える。
It is fair to say that this ceremony is part of Japan's culture.
あのビルは日本一（にっぽんいち）高（たか）いビルだと言（い）える。
One could say that the building over there is the tallest building in Japan.
と言（い）える is regularly seen paired with grammar patterns like
だろう, or
でしょう. This makes the overall statement more friendly, by considering the listener's thoughts about the issue being presented.
と言（い）えるだろう can simply be translated as ‘can we not say (A)?’, or ‘(A) can be said, right?’.
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このプランは成功（せいこう）したと言（い）えるだろう。
We could say that this plan was a success, right?
タナカ選手（せんしゅ）は国民的（こくみんてき）アスリートだと言（い）えるでしょう。
Can it not be said that Tanaka is an athlete loved by everyone in the country?
When the potential form of 言（い）う is linked with the 助動詞（じょどうし） (auxiliary verb) よう, it creates a much stronger phrase that is similar to ‘let it be said that (A)’.
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人（ひと）が話（はな）しているときに、携帯（けいたい）を見（み）るのは失礼（しつれい）だといえよう。
Let it be said that looking at your phone while someone is talking to you is rude. (Anyone would say this, so don’t make me say it to you)
The speaker is usually relatively confident about their statement when using と言（い）える, but the usage of a form that expresses conjecture shows that they are open to the possibility of being wrong, thus softening the tone.