The US patent still exists. Ordinarily, you can sue anyone for anything. Even if the patent was transferred to a Canadian, the patent would still exist and it w

The US patent still exists. Ordinarily, you can sue anyone for anything. Even if the patent was transferred to a Canadian, the patent would still exist and it would still be possible to sue its owners in US court. One major exception to this are Indian Nations. US courts have no jurisdiction due to sovereign immunity. I am not a lawyer.