Taking part in elections in a modern democratic system and voting for a candidate is not in any way comparable to giving Bay`ah. Bay`ah in Islamic political system is swearing allegiance to a ruler who commits himself to govern by the Shari`ah.
Islamic Shari`ah applies only to Muslims; so, it does not apply to predominantly non-Muslim countries.
Voting in a democratic system is, therefore, different. Muslims ought to participate in the democratic process to safeguard their interests as well as to contribute to the country as good citizens.
Your statement that some of the previous presidents of America in their foreign policies were apparently targeting Muslims makes it even more important for Muslims to get involved in the system so that they can work to reverse such policies.
For further details, please refer to the detailed answer posted here:
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