Is wearing pants and American and Jewish clothes Halal or Haram? In Hadith it is said: "A man who behaves like another man will be standing with him on the day of Qiyammah" .

Praise be to Allah, the Lord of the World; and may His blessings and peace be upon our Prophet Muhammad and upon all his Family and Companions.

We do not know any Hadith with the words that the one who behaves like others will stand with them on the Day of Judgment. But, what is proved from the Prophet (Sallallahu Alaihi wa Sallam) is that he said: "Everyone who imitates some people is one of them" [ Abu Dawood and Ahmad ].
It is narrated from Abdullah Ibn Umar that he said: 'Whoever builds in the territory of polytheists and celebrates the Persian new year's day or their carnival and imitates them till his death, he will be resurrected with them on the Day of Judgment' .
The expression 'one of them' means he will become like them in the act of the imitation; if he imitates them in their Kufr then he commits Kufr; if he imitates them in other than Kufr then his sin will be according to that.
As for wearing pants, we perceive that it is not considered as imitating non-Muslims since the prohibition of imitation means imitating them in their peculiar characteristics.
The customs that have become widely spread and common and are no longer considered as peculiar characteristics of non-Muslims are not considered as imitating non-Muslims. Therefore, wearing pants for men is permissible. However, it is preferred for a Muslim to imitate pious and knowledgeable people in their appearance and dress, if it does not cause any harm to him. Know that imitation of anyone in external matters is likely to bring love and affection for them to the heart.
Allah knows best.