Yes, you can enter the US with your B1/B2 visa for visiting purposes before processing your SIV case, as long as:
1. Your B1/B2 visa is valid and won't expire soon.
2. You meet all standard US entry requirements (e.g., proof of ties to your home country, financial support, etc.).
3. You disclose your withdrawn asylum case in Canada and your ongoing SIV case during the US immigration process, if asked.
4. You enter the US at a designated port of entry (e.g., airport, land border, or sea port).
5. You don't intend to stay in the US beyond the terms of your B1/B2 visa (typically 6 months or less).
Keep in mind:
- US immigration authorities may ask about your withdrawn asylum case and ongoing SIV case, so be prepared to provide supporting documents and information.
- Ensure your SIV case is still active and not closed or denied.
- If you have any additional immigration issues or concerns, consider consulting an immigration lawyer before traveling.
Assuming you meet these conditions, you should be able to enter the US with your B1/B2 visa for visiting purposes while your SIV case is processed. Safe travels!