原因・理由N2
〜あまり（に）
due to excessive... / because of too much...
Structure
V-た形 + あまり（に）；N + の + あまり（に）
Explanation
Indicates that because the degree was excessive, a certain result followed. Attached to 〜の, 〜た, or emotion/state nouns (驚き, 心配, 感激). The result is often an uncontrollable reaction.
Examples
驚きのあまり、何も言えませんでした。
I was so surprised that I couldn't say anything.
仕事が忙しすぎるあまり、体を壊してしまった。
He was so busy with work that he ruined his health.
Note
あまり(に) derives from "excess"; it differs from the degree adverb あまり〜ない (not very). The result is often negative or a strong reaction.
Related Grammar
〜あまり、〜ない〜ほど