What 居酒屋 refers to depends on the context.
In its broader sense, 居酒屋 includes any types of pubs, saloons, bars and the like in the world where ordinary local adults casually gather and enjoy alcohol and food. Pubs are typically referred to as "British-style 居酒屋." Take a look at 居酒屋 on Japanese Wikipedia, and it extensively explains how 居酒屋 look like and how they developed in European, Arabian, or Asian countries.
In its narrower sense, however, 居酒屋 only refers to so-called "Japanese izakaya", which typically serve yakitori, edamame, tempura, sashimi, etc., along with some non-Japanese food like pizza. (Many 居酒屋 today are heavily influenced by Western culture and are no longer equipped with tatami or red chōchin.) When Japanese people hear 居酒屋 without any context, they would have almost the same thing as so-called "Japanese izakaya" in mind.
There are many Western-style "pubs" in Japan (like this), too, and they mainly identify themselves as パブ, バル, 酒場, etc. We often just say お店 instead of 居酒屋 to vaguely include everything; one can say "来週の歓迎会で使うお店を探しておいて", and this お店 refers to everything from Japanese izakaya to Chinese restaurants to Hooters to beer gardens.