Answer
Wa `alaykum as-salamu wa rahmatullahi wa barakatuh.
In the Name of Allah, Most Gracious, Most Merciful.
All praise and thanks are due to Allah, and peace and blessings be upon His Messenger.
Dear brother, we really appreciate your question and thank you for it as it shows your concern to eat halal foods.
As for your question, you have to eat halal meat and chicken as long as they are available; meat or chicken that are not certified as halal are only allowed in certain circumstances.
In his response to your question, Sheikh Ahmad Kutty, a senior lecturer and an Islamic scholar at the Islamic Institute of Toronto, Ontario, Canada, states:
If you have clear halal alternatives, then you should not make use of this concession. For the Prophet (peace and blessings be upon him) ordered us to leave that which is doubtful.
The issue of the meat in supermarkets which are not certified as halal is controversial. Even if we follow the opinion of imams such as Imam Malik and Shafi`i, it is still doubtful in the sense that nowadays people in these countries are more secular than religious.
Therefore, it is best to avoid them, unless one has no alternative. The Prophet (peace and blessings be upon him) said, “Leave that which is doubtful in favour of that which is not doubtful.” (At-Tirmidhi)
Allah Almighty knows best.