Sometimes (many times) that in the company's terms of service or invoice or contract - they have a "jurisdictional" clause limiting any disputes are to be litigated in a specific place (usually their local court) and what law applies (usually their state's law applies).
Too, the company's terms of service can mandate arbitration or mediation
However, they didn't do that in your case and completely breached their agreement with you.
1st, they didn't comply with the original time frame of 6 weeks.
2nd, that although you came to subsequent agreement with them - they again breached that agreement by not delivering the product (furniture) within a reasonable time nor responded to your communcation.
3rd, they did not respond to your communcations and given their history - you reasonably believed that they wouldn't deliver the furniture in the near future. That you had already been waiting a long time - long after their original promise of delivery.
They didn't meet the 2nd promise of delivery.
As such, you were absolutely within your legal rights to cancel the contract with them.
I would send the company a responsive letter stating the aforesaid.
Moreover, they would have to file suit against you where you live - in CA.
They would have to retain legal representation if they are a corporation - because corporations are fictitious entities and can't represent themself.
I don't think you have anything to worry about whatsoever - you have clear defenses against any of their potential claims.
What you might to is - if you haven't already purchased other furniture - is offer them a substantial reduction to take the furniture (if you could still use it).
Otherwise, I would inform them that because of their lack of communcation, lack of due diligence, breach of contract - you canceled the contract per your email.