Can I travel to USA right now if I didn't turn in I-94 A?

Here's the situation: I've had the I-94 A which was valid for half a year, during that time I've been to USA twice (from Canada) and since no one ever tells you where to return it or that you even should, I didn't. (Btw if anyone can tell me for next time—where do you actually return it, who do you talk to, etc?)

Now, my I-94 A expired on December 3rd, but I want to travel to USA in the next few days. Is it possible to do anything now—I can provide proof that I have been back in the country for quite some time (bank statements)—or do I have to mail it to ACS with the proof and I'm stuck in Canada until then. Is there any way to return it upon my travel to USA—maybe at the border?

First of all, the last time you leave the US before your I-94 expires, you should turn it in to USCBP. If you are crossing at a land border like Port Huron, Detroit, or Buffalo, you can either stop before you cross the bridge and return it to US Customs or you can turn it in to Canadian Customs and they will return it to us. If you are flying out of the US, you can turn it in to US Customs at the US airport or most Canadian international airports have US Customs officers working there. Next question.
You should have no problem coming back to the US as long as your passport and visa have not expired. Your I-94 only expired 17days ago, that really is not a problem. When you apply for a new I-94, we will take your old one and forward it to the proper authorities.

You can turn it at the border when you return to the U.S. But expect an Officer to mention something to you about returning it.
When you leave the U.S. by car you return it to the Canadian authorities, when you leave by plane you return to the nearest Customs office in the terminal.