Which best describes this sentence?

Since many countries have football teams, there is much competition leading to the World Cup.
Compound, complex, simple or comma splice.

i would say it is a compound sentence

It's a complex sentence because it has one independent clause:

there is much competition leading to the World Cup

and one dependent (subordinate) clause:

Since many countries have football teams

The given sentence is a complex sentence.

Explanation:
A complex sentence is a sentence that contains an independent clause and at least one dependent clause. In this case, the sentence has two clauses:

1. Since many countries have football teams
- This is a dependent clause because it cannot stand alone as a complete sentence.

2. there is much competition leading to the World Cup.
- This is an independent clause because it can stand alone as a complete sentence.

The dependent clause "Since many countries have football teams" introduces a condition or reason, while the independent clause "there is much competition leading to the World Cup" presents a result or consequence.

Therefore, because the sentence consists of both an independent and dependent clause, it is classified as a complex sentence.