An item of clothing being associated to another religion may change due to place or time. By way of example, at one point in time in the Indian Subcontinent, pants and shirts were iconic of the British colonists. But in our times, if some person wears a dress pant or shirt, it does not cross an onlooker’s mind that this person is a non-Muslim or holds his allegiance to non Muslims. At the same time, while these dress pants and shirts will be permissible they would not be the ideal. This is because if an onlooker sees someone wearing pants and shirts, then although he will not think of the person as non-Muslim, at the same time he will never think of him to be an ‘Alim or an Ahl Allah. The perception of the common onlooker establishes that the dress is not those of Sulahā’ and ‘Ulamā’.[/quote]
Mufti Zameelur Rahman has also explained the matter of the Sunnah regarding clothing
here in "Question One".
Excerpt:
[quote=Mufti Zameelur Rahman]The Sunnah, in its general usage, refers to a religious practice or belief established from the Prophet (sallAllāhu ‘alayhi wasallam) and his immediate successors. If it was Sunnah to adopt the lifestyle of the place one happens to be in, why did the Sahābah fail to do this, and why did the jurists fail to record it as such?
Far from being Sunnah, it is documented from one of the most prominent Sahābah that he advised the Muslims to stick to their traditional Arab attire, and not adopt the non-Muslim dress of those around them. The senior Tābi‘ī, Abū ‘Uthmān al-Nahdī (d. 95 H), said:
“‘Umar wrote to us, while we were in Azerbaijan…[He said:] Be wary of over-indulgence, the dress of the idolaters and silk clothing…” (Sahīh Muslim)
In another version, there is the addition:
“Hold fast to the dress of your father, Ismā‘īl (‘alayhissalām).” (Sahīh Abī ‘Awānah)
At the most, it is permissible to adopt the attire of the people of a region one happens to be in, as long as it does not contravene the stipulations of Sharī‘ah. And this appears to be the Mālikī view.