What are the possible sanctions from US court if a EU company decides that continuing software patent litigation is useless but is not willing to make a deal with accusing party. In other words ignores the litigation or the court ruling if ruling is in favor of accusing party. Are there any precedents like that?

Without getting into details the patent litigation in US is so frustrating. Defending party lawyers failing to adequately represent defending party, accusing party lawyers are putting forward plain stupid/inadequate arguments... Seeking justice becomes too painful mentally and money-wise.