zyuutai no seide, basu ga nakanaka kimasen.

のせいで means because of ... or due to ..., but it usually carries a negative nuance.

So in this sentence, it means:

Because of the traffic jam, the bus isn’t coming.

Compared with more neutral cause expressions like ので or から, せいで often suggests that something bad, inconvenient, or frustrating happened.

Because せい is a noun, and nouns in Japanese often connect to other nouns with の.

The pattern is:

• noun + の + せいで

So:

• 渋滞 = traffic jam
• 渋滞のせいで = because of the traffic jam

This is the normal grammar for this expression.

が marks バス as the subject of 来ません.

So the sentence is focusing on the fact that:

the bus is the thing that is not coming.

If you said バスは, that could also be possible in some contexts, but it would sound more like you are setting the bus up as the topic, perhaps in contrast with something else.

For example:

• 電車は来ましたが、バスは来ません。
  The train came, but the bus didn’t.

In the original sentence, が is a natural choice because it simply identifies what is not coming.

With a negative verb, なかなか often means:

• not easily
• not readily
• not for a long time
• just won’t

So なかなか来ません means something like:

• is not coming for quite a while
• just isn’t coming
• doesn’t come بسهولة / readily
  (in natural English: the bus is taking a long time to come)

It adds the feeling that the speaker has been waiting and the bus still has not arrived.

Very often, yes, especially at beginner level.

A very common pattern is:

• なかなか + negative verb

Examples:

• なかなか分かりません。 = I can’t understand it easily.
• なかなか寝られません。 = I can’t fall asleep easily.

With a positive verb, なかなか can also be used, but it has a different meaning, often something like quite, fairly, or better than expected:

• なかなかおいしいです。 = It’s quite tasty.

So in your sentence, the negative 来ません is important for the meaning.

来ません is the polite negative form of 来る (to come).

Forms:

• dictionary form: 来る
• plain negative: 来ない
• polite negative: 来ません

So this sentence is in a polite style:

• 渋滞のせいで、バスがなかなか来ません。

A plain-style version would be:

• 渋滞のせいで、バスがなかなか来ない。

Both mean the same basic thing, but 来ません sounds more polite.

来る is an irregular verb.

Its main forms are:

• 来る = くる
• 来ます = きます
• 来ません = きません
• 来ない = こない

So the reading changes depending on the form. This is normal for this verb, even though it can feel strange at first.

Yes, you could say:

• 渋滞で、バスがなかなか来ません。

This also means Because of the traffic jam, the bus isn’t coming / is taking a long time to come.

The difference is nuance:

• 渋滞で = more neutral, just stating the cause
• 渋滞のせいで = stronger, more like because of the traffic jam with a feeling of inconvenience or blame

So のせいで sounds a little more emotionally loaded.

Usually, yes. It tends to be used when the cause leads to something negative, annoying, or unfortunate.

Examples:

• 雨のせいで、試合が中止になりました。
  The game was canceled because of the rain.
• 寝不足のせいで、頭が痛いです。
  I have a headache because of lack of sleep.

For positive or neutral reasons, Japanese usually prefers other expressions such as:

• ので
• から
• sometimes just で

So せいで is a good clue that the result is something undesirable.

Because 来る (to come) is an intransitive verb.

That means it does not take a direct object.

In English, come also works this way:

• We say The bus comes
• Not The bus comes something

So in Japanese:

• バスが来ます = The bus comes

The bus is the subject, so it takes が, not を.

The comma shows a natural pause:

• 渋滞のせいで、｜バスがなかなか来ません。

It separates the cause part from the main statement.

Japanese commas are often more flexible than English commas, so the sentence could also be written without one in casual writing:

• 渋滞のせいでバスがなかなか来ません。

Both are fine. The comma just makes it a little easier to read.

It is pronounced:

じゅうたい の せいで、 バス が なかなか きません。

Word by word:

• 渋滞 = じゅうたい
• のせいで = の せいで
• バス = バス
• が = が
• なかなか = なかなか
• 来ません = きません

So the full reading is:

じゅうたいのせいで、バスがなかなかきません。